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Volume Converter

Convert between metric, US customary, and UK imperial volume units (millilitre, cubic centimetre, litre, cubic metre, cubic inch, cubic foot, cubic yard, US fluid ounce, US pint, US gallon, UK pint, UK gallon) with NIST-grade exact factors.

gal

Result

3.78541 L

1 gal= 3.785412 L

UnitValue
Milliliter (mL)3,785.41
Cubic centimeter (cm³)3,785.41
Liter (L)3.78541
Cubic meter (m³)0.00378541
Cubic inch (in³)231
Cubic foot (ft³)0.133681
Cubic yard (yd³)0.00495113
US fluid ounce (fl oz)128
US pint (pt)8
US gallon (gal)1
UK pint (imperial) (pt (UK))6.66139
UK gallon (imperial) (gal (UK))0.832674

Switching between teaspoons, cups, and grams? Try the cooking converter.

Volume converter. Metric, US customary, and UK imperial units with NIST-exact factors.

A volume converter changes a value from one unit to another using exact factors from NIST SP 811 and the UK Weights and Measures Act 1985. It tells US gallons (3.785411784 L) and UK gallons (4.54609 L) apart, so litres-per-100 km figures from a UK car review do not get mistaken for the same figure under a US gallon.

What Is a Volume Converter?

A volume converter is a tool that takes a measurement in one unit of volume and returns the equivalent value in any other supported unit. Every conversion in this calculator routes through a single base unit, the cubic metre, using each unit's defined factor: 1 millilitre is exactly 1 × 10⁻⁶ m³, 1 litre is exactly 1 × 10⁻³ m³, 1 cubic foot is exactly 0.028316846592 m³, 1 US gallon is exactly 3.785411784 × 10⁻³ m³ (= 231 cubic inches), and 1 UK gallon is exactly 4.54609 × 10⁻³ m³. These are not engineering approximations; they are exact rational factors fixed by NIST SP 811 Appendix B.8 (US customary), the 1959 International Yard and Pound Agreement (imperial geometric units), and the UK Weights and Measures Act 1985 Schedule 1 (UK imperial fluid units).
This converter supports twelve units across four groups. The metric group covers the millilitre (mL), cubic centimetre (cm³), litre (L) and cubic metre (m³) — all derived from the SI definition of the metre as the distance light travels in vacuum in 1/299,792,458 of a second (in force since the 2019 SI revision). The imperial geometric group covers the cubic inch, cubic foot and cubic yard, defined by cubing the 1959 international foot (0.3048 m), yard (0.9144 m) and inch (0.0254 m). The US customary fluid group covers the US fluid ounce, US pint and US gallon, all derived from the historical wine gallon of exactly 231 in³. The UK imperial fluid group covers the UK pint and UK gallon, derived from the 1985 statutory definition of 4.54609 dm³.
What distinguishes a serious volume converter from a marketing widget is honesty about which units are interchangeable and which are not. Every metric, US customary and UK imperial volume unit in this calculator is defined by an exact rational factor to the cubic metre — so every cross-conversion in the table is mathematically exact, regardless of how irrational the printed decimal looks. The single most-confused pair, US gallon vs UK gallon, is two completely different volumes (3.785 L vs 4.546 L, a 20% delta), not a rounding question. The converter calls both out by name, never as a generic "gallon", and tags every result with an "exact" badge because every supported pair is definitionally exact.

How to Convert Between Volume Units

Every volume conversion is one multiplication and one division through the cubic metre. The general formula is:
y=x⋅afromatoy = x \cdot \frac{a_{\text{from}}}{a_{\text{to}}}
where $x$ is your input value, $a\text{from}$ is the source unit's factor to cubic metres, and $a\text{to}$ is the target unit's factor to cubic metres. To do it by hand:
1. Look up the source-to-cubic-metre factor. For US gallons, $a\text{from} = 0.003785411784$.
2. Multiply the input by that factor to get cubic metres. 5 US gal × 0.003785411784 = 0.01892705892 m³.
3. Look up the target-to-cubic-metre factor. For litres, $a\text{to} = 0.001$.
4. Divide the cubic-metre value by the target factor. 0.01892705892 ÷ 0.001 = 18.92705892 L.
The same procedure works for every supported unit. Going from cubic feet to US gallons: 1 ft³ × 0.028316846592 m³/ft³ ÷ 0.003785411784 m³/US gal = 7.48051948... US gallons. Going from UK gallons to US gallons: 1 UK gal × 0.00454609 m³/UK gal ÷ 0.003785411784 m³/US gal = 1.20095042... US gallons (the famous 1 UK gal ≈ 1.2 US gal ratio).
To use this calculator, pick the source unit from the "From" dropdown, type a value, then pick the target unit from the "To" dropdown. The result updates on every keystroke. Click the result card to copy it to the clipboard. Use the precision selector to switch between auto (6 significant figures) or a fixed 0, 2, 4, 6, 10 or 15 decimals. Auto-precision switches to scientific notation when the result is larger than 10¹² (one trillion) or smaller than 10⁻³, so converting a continent-scale volume to millilitres still renders readably. The "exact" badge appears next to every volume result, because every unit in this set has a rational, definitionally exact factor to the cubic metre.

Volume Conversion Formula

y=x⋅afromatoy = x \cdot \frac{a_{\text{from}}}{a_{\text{to}}}
  • yy = The converted value, expressed in the target unit of volume.
  • xx = The input value, expressed in the source unit of volume.
  • afroma_{\text{from}} = Factor that converts the source unit to cubic metres (e.g. 0.001 for litres, 0.003785411784 for US gallons, 0.00454609 for UK gallons).
  • atoa_{\text{to}} = Factor that converts the target unit to cubic metres (e.g. 1e-6 for millilitres, 0.028316846592 for cubic feet).
The formula is a two-step pivot through the cubic metre base unit. The factor table this calculator uses is sourced directly from NIST SP 811 Appendix B.8, the 1959 International Yard and Pound Agreement, and the UK Weights and Measures Act 1985 Schedule 1:
  • Millilitre (mL): 1 × 10⁻⁶ m³ (exact, SI; 1 L = 1 dm³ = 10⁻³ m³ → 1 mL = 10⁻⁶ m³)
  • Cubic centimetre (cm³): 1 × 10⁻⁶ m³ (exact, SI; numerically identical to mL — both kept for UX clarity)
  • Litre (L): 1 × 10⁻³ m³ (exact, SI-accepted non-SI unit; BIPM SI Brochure)
  • Cubic metre (m³): 1 m³ (exact, SI derived unit)
  • Cubic inch (in³): 1.6387064 × 10⁻⁵ m³ (exact, = 0.0254³)
  • Cubic foot (ft³): 0.028316846592 m³ (exact, = 0.3048³; boldfaced in NIST SP 811)
  • Cubic yard (yd³): 0.764554857984 m³ (exact, = 0.9144³)
  • US fluid ounce (fl oz): 2.95735295625 × 10⁻⁵ m³ (exact, = 231/128 in³ = 29.5735295625 mL)
  • US pint (pt): 4.73176473 × 10⁻⁴ m³ (exact, = 1/8 US gal)
  • US gallon (gal): 3.785411784 × 10⁻³ m³ (exact, = 231 in³ × 2.54³ cm³/in³)
  • UK pint (pt UK): 5.6826125 × 10⁻⁴ m³ (exact, = 1/8 UK gal, derived from the 1985 statutory definition)
  • UK gallon (gal UK): 4.54609 × 10⁻³ m³ (exact, UK W&MA 1985 Schedule 1 Part VI: "GALLON = 4.54609 cubic decimetres")
For the m³ → cubic-foot direction the calculator displays the irrational quotient 1/0.028316846592 = 35.31466672148858… ft³/m³. Most casual converters print 35.3147 and stop there; this one will print as many digits as the precision selector requests, up to 15. The same applies to the US-gallon-per-cubic-foot quotient: 0.028316846592 / 0.003785411784 = 7.48051948051948… US gal per ft³ (a repeating rational, since 0.028316846592 / 0.003785411784 = 1728/231 exactly when you trace both factors back to in³). Every result is tagged exact because both endpoints are exact rationals.

Worked Volume Conversion Examples

5 US gallons to litres (the daily fuel question)

Set From = US gallon, To = Liter, Value = 5. The formula gives 5 × 3.785411784 = 18.92705892 L exact. At auto-precision the result reads 18.9271 L (6 significant figures). A typical US gas pump round-trip of 5 gallons fills almost exactly 19 litres — useful when a US driver crosses into Canada or Mexico and the pump display switches to litres. Both endpoints (US gallon, litre) are defined by exact rational factors to the cubic metre, so the conversion has zero rounding error: the answer is mathematically exact, not just precise.

1 UK gallon to US gallons (the most-confused conversion)

Set From = UK gallon (imperial), To = US gallon, Value = 1. The formula gives 0.00454609 / 0.003785411784 = 1.20095042… US gallons. At auto-precision the result reads 1.20095 US gal. This is the conversion every US visitor to the UK has to do mentally at the petrol pump: one imperial gallon is about 20% larger than one US gallon. Inverted: 1 US gal ÷ 1 UK gal ≈ 0.8327 — a US gallon is roughly 83% of a UK gallon, not the other way around. The two are completely different volumes (3.785 L vs 4.546 L), defined separately in NIST SP 811 and the UK W&MA 1985, and a single "gallon" with no nationality is ambiguous in any technical document.

1 cubic foot to US gallons (concrete, water tanks, HVAC)

Set From = Cubic foot, To = US gallon, Value = 1. The formula gives 0.028316846592 / 0.003785411784 = 7.480519480519… US gallons (a repeating rational since the underlying ratio is 1728/231 in cubic inches). At auto-precision the result reads 7.48052 US gal. This is the constant every plumber, swimming-pool installer and concrete contractor in the US memorises: one cubic foot of water is just under 7½ US gallons. Set precision to 15 decimals to see 7.480519480519481 — the full IEEE-754 double, with the repeating decimal truncated at the mantissa boundary. Useful when you are checking a tank-volume formula against a CAD model.

100 mL to US fluid ounces (the cooking conversion)

Set From = Milliliter, To = US fluid ounce, Value = 100. The formula gives 100e-6 / 2.95735295625e-5 = 3.3814022701… fl oz. At auto-precision the result reads 3.38140 fl oz. A typical European recipe calling for 100 mL of milk translates to about 3⅜ US fluid ounces; for nutrition-label work, US food regulations define a "common household" fluid ounce as exactly 30 mL (21 CFR §101.9), so a 100 mL serving rounds to 3.3 "label ounces" rather than the precise 3.381 customary ounces. For recipe-scale work the 30 mL/oz shortcut is fine; for chemistry or pharmacy use the exact 29.5735295625 mL value.

1 cubic yard to cubic feet (concrete-order arithmetic)

Set From = Cubic yard, To = Cubic foot, Value = 1. The formula gives 0.764554857984 / 0.028316846592 = 27 ft³ exact. This is one of the cleanest constants in the imperial set: 1 yd³ = 3³ ft³ = 27 ft³ exactly, by the cube of the 1959 yard-to-foot ratio (1 yd = 3 ft exactly). Every concrete contractor in the US works in cubic yards, every blueprint in cubic feet — and the 27 multiplier lets you flip between the two in your head. A typical 10 ft × 10 ft × 4 in slab is 10 × 10 × (4/12) = 33.33 ft³ = 1.235 yd³ of concrete, plus a 10–15% waste allowance.

Comparative table: 1 unit in cubic metres and litres

UnitValue in m³Value in LEquivalent in US galEquivalent in UK galExact?
Millilitre (mL)1e−60.0012.6417e−42.1997e−4yes
Cubic centimetre (cm³)1e−60.0012.6417e−42.1997e−4yes
Cubic inch (in³)1.6387064e−50.0163870644.3290e−33.6047e−3yes
US fluid ounce (fl oz)2.9573530e−50.0295735307.8125e−3 (=1/128)6.5053e−3yes
UK fluid ounce2.8413063e−50.0284130637.5060e−36.25e−3 (=1/160)yes
US pint (pt)4.7317647e−40.4731764730.125 (=1/8)0.10408yes
UK pint (pt UK)5.6826125e−40.568261250.150120.125 (=1/8)yes
Litre (L)1e−310.264170.21997yes
US gallon (gal)3.785411784e−33.78541178410.83267yes
UK gallon (gal UK)4.54609e−34.546091.200951yes
Cubic foot (ft³)2.8316847e−228.3168477.480526.22884yes
Cubic yard (yd³)7.6455486e−1764.55486201.974168.179yes
Cubic metre (m³)11000264.172219.969yes
Three definitional shortcuts worth memorising: 1 US gal = 128 fl oz = 231 in³ exactly; 1 UK gal = 160 fl oz UK = 4.54609 L exactly; 1 ft³ = 1728 in³ = 27 ft³ per yd³ exactly. All other rows are exact rationals that follow from these definitions and the 1959 yard.

Most common volume conversions

These are the unit pairs people look up most often. Use them as a quick reference, or paste them into the calculator for an exact result to 15 decimals.
  • Litres to US gallons: 1 L = 0.264172 gal US
  • US gallons to litres: 1 gal US = 3.785412 L (exact)
  • Litres to UK gallons: 1 L = 0.219969 gal UK
  • UK gallons to litres: 1 gal UK = 4.54609 L (exact)
  • US gallons to UK gallons: 1 gal US = 0.832674 gal UK
  • UK gallons to US gallons: 1 gal UK = 1.20095 gal US
  • Litres to US fluid ounces: 1 L = 33.8140 fl oz US
  • US fluid ounces to millilitres: 1 fl oz US = 29.5735 mL (exact)
  • US pints to millilitres: 1 pt US = 473.176 mL (= 1/8 US gal)
  • UK pints to millilitres: 1 pt UK = 568.261 mL (= 1/8 UK gal)
  • Cubic metres to litres: 1 m³ = 1,000 L (exact)
  • Cubic feet to litres: 1 ft³ = 28.3168 L
  • Cubic inches to millilitres: 1 in³ = 16.3871 mL (exact)
  • Cubic yards to cubic metres: 1 yd³ = 0.764555 m³
  • Millilitres to US fluid ounces: 1 mL = 0.033814 fl oz US

Volume Conversion Tips

  • Always disambiguate US vs UK gallon. The same word "gallon" with no nationality is meaningless in any technical document: 1 US gal = 3.785411784 L and 1 UK gal = 4.54609 L are two completely different volumes. A car review printed in the UK as "40 mpg" works out to 33.3 mpg US (×0.8327) — the US number is about 17% lower because the UK gallon is about 20% larger (the two percentages are inverse, not the same). This calculator labels both units explicitly in the dropdown — never trust a converter that lets you pick "gallon" without a flag.
  • Memorise the five exact pivots through the cubic metre: millilitre (1e-6), litre (1e-3), cubic foot (0.028316846592), US gallon (0.003785411784) and UK gallon (0.00454609). Every conversion in this tool is implemented as "input × from-factor ÷ to-factor", so memorising these five gives you the entire cross-table in your head. The cubic inch (1.6387064e-5) and cubic yard (0.764554857984) round out the set for surveying and concrete work.
  • Treat 1 mL = 1 cm³ as definitionally exact, not a coincidence. Since the 1964 CGPM redefinition, the litre is exactly 1 dm³ = 1000 cm³, so 1 mL = 0.001 L = 1 cm³ by construction. Medical syringes, engine displacement (cc), pharmacy dosing, and chemistry lab volumes all use the two units interchangeably; the calculator keeps both for UX clarity, but converting between them is the identity transform.
  • Use the precision selector to match your audience. Recipe and grocery work rounds to whole millilitres or fluid ounces (a 250 mL cup is rarely advertised as 8.4535 fl oz). Petroleum tank-truck volumes and HVAC ductwork take-offs work to 2-4 decimal cubic feet. Fluid-dynamics engineers verifying a CFD mesh want 10 decimals; metrologists comparing against a primary water-volume standard want 15 (the full IEEE-754 double). Switching at the model's last step keeps the rounding error out of the intermediate math.
  • Every volume unit in this set is exact. Unlike length conversions involving the light-year or parsec, where IAU definitions exceed 64-bit double precision, every volume factor here is a finite rational that fits cleanly in IEEE-754: 1e-6, 1e-3, 1, 1.6387064e-5, 0.028316846592, 0.764554857984, 2.95735295625e-5, 4.73176473e-4, 3.785411784e-3, 5.6826125e-4, 4.54609e-3 — all exact. The "exact" badge fires for every pair.
  • Watch for the "30 mL fluid ounce" trap in US nutrition labels. US food regulation 21 CFR §101.9(b)(5)(viii) defines a "common household" fluid ounce as exactly 30 mL for serving-size declarations, not the customary 29.5735295625 mL — a 1.44% difference. The package size is still labeled in customary fluid ounces, but the per-serving column is built around the rounded 30 mL number. This calculator uses the customary fluid ounce; for label compliance work, divide by 30 instead.
  • Cubic-foot ↔ US-gallon work hinges on 1 ft³ = 7.48052 US gallons (exactly 1728/231). Plumbers, pool installers and HVAC designers use this constant to convert water-tank dimensions (ft³) into bill-of-materials units (gallons). For UK work the equivalent is 1 ft³ = 6.22884 UK gallons. Both are exact rationals; pick the one that matches your gallon flavor and the rest of the math is automatic.
  • When the result is larger than 10¹² (one trillion) or smaller than 10⁻³ at auto-precision, the display switches to scientific notation. This is on purpose: writing 1 m³ in millilitres as 1,000,000 mL is fine but 1 km³ in mL would be 1,000,000,000,000,000 mL — unreadable, while 1e15 mL is parseable at a glance.
  • For teaspoons, cups, tablespoons and grams in a cooking context, use the dedicated cooking converter (/en-US/tools/cooking-converter). This volume converter targets engineering, fuel, industrial and scientific conversions where exact NIST factors matter; the cooking tool handles density-aware conversions (e.g. 1 cup of flour ≠ 1 cup of water by mass) that are out of scope here.

Volume Converter — Frequently Asked Questions

Is this volume converter free?

Yes. The calculator is free, requires no account, runs entirely in your browser, and is ad-free. The embeddable iframe version at /en-US/widget/volume-converter is also free and ad-free, so you can drop it into engineering portals, plumbing-trade sites, brewing forums or school materials without exposing readers to third-party trackers.

How accurate are the volume conversion factors?

Every factor in this converter is exact. The metric factors are exact by SI definition. The imperial geometric factors (cubic inch, cubic foot, cubic yard) are exact rationals derived from the 1959 International Yard and Pound Agreement. The US customary fluid factors (US fluid ounce, US pint, US gallon) are exact rationals from NIST SP 811 Appendix B.8, ultimately derived from the historical wine gallon of exactly 231 cubic inches. The UK imperial fluid factors (UK pint, UK gallon) are exact by the UK Weights and Measures Act 1985, which fixed the gallon at exactly 4.54609 litres.

Is 1 millilitre the same as 1 cubic centimetre?

Yes, exactly. Since the 1964 CGPM redefinition, 1 litre = 1 dm³ exactly, so 1 mL = 1 cm³ by definition. Both equal 10⁻⁶ m³. We keep both in the converter because users searching for "mL" or "cm³" shouldn't have to know they're identical.

What is the difference between a US gallon and a UK gallon?

A US gallon is exactly 3.785411784 litres (= 231 cubic inches, a figure traced to the 1706 Queen Anne wine gallon and legally adopted as the US standard in 1836). A UK (imperial) gallon is exactly 4.54609 litres (defined by the UK Weights and Measures Act 1985). The UK gallon is about 20% larger; equivalently, a US gallon is about 83.27% of a UK gallon. The two are not roundings of each other — they are different units with separate legal definitions. A fuel-economy figure quoted in UK miles-per-gallon is roughly 20% better than the same number under US gallons would be.

How many litres are in a US gallon?

Exactly 3.785411784 litres. The 231-in³ figure traces to the 1706 Queen Anne wine gallon and was legally adopted as the US standard gallon in 1836. Its exact metric value follows from the 1959 International Yard and Pound Agreement, which fixed the cubic inch at 0.0254³ = 1.6387064 × 10⁻⁵ m³, so 231 × 1.6387064e-5 = 0.003785411784 m³ = 3.785411784 L exactly. Most casual references quote 3.785 L or 3.79 L, which are five- and three-significant-figure roundings.

How many litres are in a UK gallon?

Exactly 4.54609 litres. The UK Weights and Measures Act 1985, Schedule 1, Part VI defines the imperial gallon as exactly 4.54609 cubic decimetres. This is not a rounding of an older definition — it is the binding statutory value in force in the United Kingdom and several Commonwealth/Caribbean countries that still use the imperial gallon for fuel.

How many fluid ounces in a US gallon?

Exactly 128 US fluid ounces. The relationship is definitional: 1 US gal = 4 quarts = 8 pints = 128 fluid ounces. In litres that works out to 128 × 29.5735295625 mL = 3785.411784 mL = 3.785411784 L exactly. For the UK system the equivalent is 1 UK gal = 160 imperial fluid ounces × 28.4130625 mL = 4546.09 mL = 4.54609 L exactly.

What is 1 cubic foot in US gallons?

Exactly 7.480519480519… US gallons (a repeating rational, since 0.028316846592 m³ ÷ 0.003785411784 m³/gal = 1728/231 in³/in³). For everyday plumbing and pool work, the 7.48 constant is enough. For the UK system the equivalent is 1 ft³ = 6.22884 UK gallons. Both ratios are exact because both endpoints are defined exactly.

Why does 1 cubic metre to cubic feet give an irrational decimal?

Because the exact definition runs the other way: 1 cubic foot is exactly 0.028316846592 m³. The inverse 1/0.028316846592 = 35.31466672148858… ft³/m³ is mathematically irrational — there is no last digit, only a longer truncation. Engineering and surveying tables almost always print 35.3147; this calculator will show whatever precision you ask for, up to 15 decimal digits.

How many cubic feet in a cubic yard?

27 cubic feet exactly. Since the 1959 yard fixes 1 yd = 3 ft exactly, 1 yd³ = 3³ ft³ = 27 ft³ exactly. Concrete contractors use this constant to flip between blueprint cubic feet (formwork) and truck-order cubic yards (delivery slips).

What is a US pint versus a UK pint?

A US (liquid) pint is exactly 1/8 of a US gallon = 473.176473 mL. A UK (imperial) pint is exactly 1/8 of a UK gallon = 568.26125 mL. The UK pint is about 20% larger — a beer poured "as a pint" in a UK pub is meaningfully bigger than the same drink poured "as a pint" in a US bar. Both pints are exact, because both gallons are exact and the 1/8 ratio is definitional.

Can I embed this volume converter on my site?

Yes. The embeddable version lives at /en-US/widget/volume-converter; copy the iframe snippet from the embed page. The iframe is ad-free, dependency-free, mobile-responsive, and inherits no third-party trackers — useful for engineering portals, plumbing- and HVAC-trade sites, home-brewing forums, and STEM-education pages that need a converter without ad noise.

Why are the US fluid ounce and the imperial fluid ounce different?

Because each is defined as a fraction of a different gallon. 1 US fl oz = 1/128 of a US gallon = 29.5735295625 mL exactly. 1 imperial fl oz = 1/160 of a UK gallon = 28.4130625 mL exactly. The US ounce is actually about 4.084% larger than the imperial ounce, even though the UK gallon is the larger of the two gallons — because the UK gallon is divided into 160 fluid ounces instead of 128. This calculator implements the US fluid ounce; for nutrition-label work the FDA's "common household" 30 mL shortcut is also worth knowing.

Key Volume Conversion Terms

Cubic metre (m³)

The SI derived unit of volume, defined as the volume of a cube one metre on a side. Since the 2019 SI revision the metre itself is fixed via the speed of light, so the cubic metre inherits that definitional precision. Standard for industrial, engineering and scientific volume reporting. Wikidata: Q25517.

Litre (L)

A non-SI unit of volume accepted for use with the SI, equal to exactly 1 cubic decimetre (1 L ≡ 1 dm³ ≡ 0.001 m³) since the 1964 CGPM redefinition. Replaced the older 1901 definition (volume of 1 kg of water at maximum density ≈ 1.000028 dm³). Listed on the BIPM SI Brochure accepted non-SI list. Wikidata: Q11582.

Millilitre (mL)

One thousandth of a litre, equal to exactly 1 × 10⁻⁶ m³. Physically identical to the cubic centimetre (1 mL = 1 cm³ exactly) by the 1964 litre redefinition. Standard for liquid medicine, cooking, fuel, and household-scale volumes worldwide.

Cubic centimetre (cm³, cc)

The volume of a cube one centimetre on a side, equal to exactly 1 × 10⁻⁶ m³ and physically identical to the millilitre. Standard in engineering (engine displacement is quoted in cc), pharmacology (syringes are calibrated in cc), and biology (small-vessel anatomy).

US gallon (US gal)

A US customary unit of liquid volume equal to exactly 231 cubic inches = 3.785411784 litres = 3.785411784 × 10⁻³ m³. The 231-in³ figure traces to the 1706 Queen Anne wine gallon (English statute), legally adopted as the US standard gallon in 1836; its exact metric value follows from the 1959 International Yard and Pound Agreement, which fixed the inch at exactly 0.0254 m. Used in the United States for fuel, milk, paint and large-volume retail packaging. Wikidata: Q23925413.

UK gallon / imperial gallon (UK gal)

A UK imperial unit of volume equal to exactly 4.54609 litres = 4.54609 × 10⁻³ m³, defined by the UK Weights and Measures Act 1985, Schedule 1, Part VI: "GALLON = 4.54609 cubic decimetres". Used in the UK and several Commonwealth and Caribbean countries for fuel and beverages. About 20% larger than the US gallon. Wikidata: Q23925410.

Cubic foot (ft³)

An imperial/US customary unit of volume equal to exactly 0.028316846592 m³ (= 0.3048³), boldfaced as exact in NIST SP 811 Appendix B.8. Equal to exactly 1728 in³ and to 7.480519480… US gallons or 6.22884 UK gallons. Standard for water-tank, HVAC, refrigeration and natural-gas (mcf, ccf) volumes in the US. Wikidata: Q1545979.

Cubic yard (yd³)

A US/imperial unit of volume equal to exactly 0.764554857984 m³ (= 0.9144³). Equal to exactly 27 cubic feet by the cube of the 1959 yard-to-foot ratio. Standard for concrete and bulk-aggregate orders in the US construction industry.

Cubic inch (in³)

An imperial unit of volume equal to exactly 1.6387064 × 10⁻⁵ m³ (= 0.0254³). The historical basis of the US gallon definition (1 US gal = 231 in³ exactly). Still used in US automotive engine displacement ("a 350 in³ small-block V8") and in some legacy plumbing standards.

US fluid ounce (fl oz)

A US customary unit of volume equal to 1/128 of a US gallon = 29.5735295625 mL exactly. Distinct from the imperial fluid ounce (28.4130625 mL) and from the FDA "common household" fluid ounce (exactly 30 mL, used only for nutrition-label serving sizes per 21 CFR §101.9). Wikidata: Q420266.

Exact factor

A conversion factor fixed by international definition or national legislation, with zero rounding error. For volume, every factor in this calculator is exact: 1 mL = 1e-6 m³, 1 L = 1e-3 m³, 1 US gal = 3.785411784e-3 m³, 1 UK gal = 4.54609e-3 m³, 1 ft³ = 0.028316846592 m³. NIST SP 811 Appendix B.8 prints exact factors in boldface.

International Yard and Pound Agreement (1959)

Multilateral agreement signed by the US, UK, Canada, Australia, New Zealand and South Africa, effective 1 July 1959. It defined the yard as exactly 0.9144 m. Every imperial geometric volume unit in this calculator (cubic inch through cubic yard) derives its exact metric value from this single agreement.

UK Weights and Measures Act 1985

The UK statute that consolidated the definitions of imperial and metric units for trade and commerce. Schedule 1, Part VI fixes the gallon as exactly 4.54609 cubic decimetres, the binding statutory definition still in force in the UK.

Significant figures

The digits in a numerical result that carry meaning about its precision. Auto-precision in this calculator targets 6 significant figures, the default for engineering tables. NIST SP 811 volume factors are typically quoted to 7 significant figures so that any rational rounding of an exact factor is unambiguous.

Scientific notation

A way of writing very large or very small numbers as a coefficient times a power of ten, e.g. 1 km³ = 1 × 10¹⁵ mL. The calculator switches to this notation automatically when results fall outside the 10⁻³ to 10¹² range, so a continent-scale water-budget figure in millilitres remains readable.

Sumber dan Rujukan

  1. NIST SP 811 Appendix B.8 — Factors for units listed alphabetically (exact volume factors in boldface: US fluid ounce 2.95735295625e-5 m³, US gallon 3.785411784e-3 m³, cubic foot 2.8316846592e-2 m³, all definitionally exact)
  2. NIST Guide to the SI, Appendix B — Conversion factors (landing page, with the canonical bold-is-exact convention)
  3. BIPM — The International System of Units (SI Brochure, 9th edition 2019): the litre is listed among non-SI units accepted for use with the SI (1 L ≡ 1 dm³ ≡ 0.001 m³, exact)
  4. UK Weights and Measures Act 1985, Schedule 1, Part VI — "GALLON = 4.54609 cubic decimetres"; the binding statutory definition of the imperial gallon in force since 1985
  5. Wikipedia — Gallon: US gallon defined as exactly 231 cubic inches = 3.785411784 L; imperial gallon = 4.54609 L exactly since the 1985 UK Weights and Measures Act; ratio 1 UK gal ≈ 1.20095 US gal (US gal is ~83.27% of UK gal)
  6. Wikipedia — Litre: SI-accepted non-SI unit, defined as 1 L ≡ 1 dm³ ≡ 1000 cm³ since the 1964 CGPM redefinition (replacing the older 1.000028 dm³ mass-based definition); 1 mL ≡ 1 cm³ exactly
  7. Wikipedia — Fluid ounce: US fluid ounce = 1/128 US gallon = 29.5735295625 mL exactly; imperial fluid ounce = 1/160 UK gallon = 28.4130625 mL exactly; US fl oz is ~4.084% larger than the imperial fl oz despite the UK gallon being larger overall
  8. Wikipedia — International Yard and Pound Agreement (1 July 1959): yard defined as exactly 0.9144 m → cubic foot exactly 0.028316846592 m³, cubic yard exactly 0.764554857984 m³, cubic inch exactly 1.6387064e-5 m³

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