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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

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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 a litres-per-100 km figure from a UK car review is never mistaken for the same figure under a US gallon.

What Is a Volume Converter?

Why does "1 gallon" mean two different amounts of fuel? Fill a US tank to 1 gallon and you have 3.785411784 litres; fill it to 1 UK (imperial) gallon and you have 4.54609 litres — about 20% more liquid for the same word. That gap is not a rounding error: it is the single most expensive ambiguity in everyday measurement. It quietly ruins American recipes scaled in British kitchens, makes a UK "40 mpg" car look thirstier than it is when read as US miles-per-gallon, and throws off home-brewing and fuel-economy comparisons whenever someone copies a number without checking which gallon it belongs to. The fluid ounce hides the same trap one level down: a US fluid ounce is 29.5735295625 mL while a UK fluid ounce is 28.4130625 mL, so even "a few ounces" of a marinade or a cocktail measure depends on which side of the Atlantic the recipe was written.
This calculator removes the guesswork by routing every conversion through one base unit — the cubic metre — instead of storing a tangled web of unit-to-unit pairs. Each unit carries one defined factor to that base: 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. To convert, the tool multiplies your input by the source factor to reach cubic metres, then divides by the target factor. Because both endpoints are exact rational numbers fixed by international definition — NIST SP 811 Appendix B.8 for US customary units, the 1959 International Yard and Pound Agreement for the geometric units, and the UK Weights and Measures Act 1985 for the imperial fluid units — every result is mathematically exact, no matter how irrational the printed decimal looks.
Twelve units are supported, in four groups. The metric group covers the millilitre (mL), cubic centimetre (cm³), litre (L) and cubic metre (m³). The imperial geometric group covers the cubic inch, cubic foot and cubic yard, each defined by cubing the 1959 international inch (0.0254 m), foot (0.3048 m) and yard (0.9144 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. The converter labels US and UK units by name in the dropdown — never a bare "gallon" — and tags every result "exact", because every supported pair has a rational, definitionally exact factor to the cubic metre.

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, afrom is the source unit's factor to cubic metres, and ato is the target unit's factor to cubic metres. To do it by hand, taking the most common lookup — US gallons into litres:
1. Look up the source-to-cubic-metre factor. For US gallons, afrom = 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, ato = 0.001.
4. Divide the cubic-metre value by the target factor. 0.01892705892 ÷ 0.001 = 18.92705892 L. At auto-precision the tool shows 18.9271 L (6 significant figures).
The same procedure works for every supported unit. Cubic feet to US gallons: 1 ft³ × 0.028316846592 ÷ 0.003785411784 = 7.48052 US gallons per cubic foot (exactly 1728/231 when you trace both factors back to cubic inches). UK gallons to US gallons: 1 UK gal × 0.00454609 ÷ 0.003785411784 = 1.20095 US gallons (the famous 1 UK gal ≈ 1.2 US gal ratio). Millilitres to US fluid ounces: 100 mL × 1e-6 ÷ 2.95735295625e-5 = 3.38140 fl oz — the standard translation of a European recipe.
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 result, because every unit in this set has a rational, definitionally exact factor to the cubic metre.

Most-Searched Volume Conversions

FromToValueExact?
1 US gallonlitres3.785412 Lyes
1 UK gallonlitres4.54609 Lyes
1 litreUS gallons0.264172 gal USyes
1 UK gallonUS gallons1.20095 gal USyes
1 m³litres1,000 Lyes
1 m³US gallons264.172 gal USyes
1 US fluid ouncemillilitres29.5735 mLyes
1 litreUS fluid ounces33.8140 fl ozyes
1 US pintmillilitres473.176 mLyes
1 UK pintmillilitres568.261 mLyes
1 cubic footlitres28.3168 Lyes
1 cubic inchmillilitres16.3871 mLyes
1 cup (US legal, kitchen)millilitres240 mLUS standard
1 tablespoon (US, kitchen)millilitres≈14.79 mLUS customary
1 teaspoon (US, kitchen)millilitres≈4.93 mLUS customary

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 = 16.387064 mL)
  • 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 = 473.176473 mL)
  • US gallon (gal): 3.785411784 × 10⁻³ m³ (exact, = 231 in³)
  • UK pint (pt UK): 5.6826125 × 10⁻⁴ m³ (exact, = 1/8 UK gal = 568.26125 mL)
  • 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 prints 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 the ratio reduces to 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 5-gallon US gas-pump fill is 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. For fuel economy, a handy rule is mpg = 235 / (litres per 100 km), so a 27 mpg US car burns about 8.7 L/100 km.

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 = 1.20095 US gallons. Inverted: 1 US gal ÷ 1 UK gal = 3.785411784 / 4.54609 = 0.83267 — a US gallon is roughly 83% of a UK gallon, not the other way around. In percentage terms, the UK gallon is about 20% larger than the US gallon; equivalently, the US gallon is about 17% smaller (the two percentages are inverse, not equal). This is the conversion every US visitor to the UK has to do mentally at the petrol pump. 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, so 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. For UK work the equivalent is 1 ft³ = 6.22884 UK gallons.

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 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.

1 oil barrel (42 US gallons) to litres (Brent and WTI)

An oil barrel on the world market is exactly 42 US gallons ≈ 158.987 litres (often rounded to 159 L). Set From = US gallon, To = Liter, Value = 42. The formula gives 42 × 3.785411784 = 158.9872949 L exact; at auto-precision it reads 158.987 L. The 42-gallon standard comes from 1866 Pennsylvania oil producers, who added 2 gallons of slack to the original 40-gallon wooden barrel to allow for evaporation and leakage in transit. It is the quoting unit for Brent (the European benchmark) and WTI (the US benchmark). The conversion is exact because both the US gallon (NIST SP 811) and the litre (BIPM) are rational factors.

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
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 imperial fl oz = 4.54609 L exactly; 1 ft³ = 1728 in³, and 1 yd³ = 27 ft³ exactly. All other rows are exact rationals that follow from these definitions and the 1959 yard. For teaspoons, tablespoons and cups in a density-aware cooking context, use the dedicated cooking converter at /en-US/tools/cooking-converter.

Volume Converter — Frequently Asked Questions

How many litres are in a gallon?

It depends on the country. A US gallon is exactly 3.785411784 litres (≈ 3.785 L); a UK (imperial) gallon is exactly 4.54609 litres (≈ 4.546 L). The UK gallon is about 20% larger — not a rounding difference, but two units with separate legal definitions. Always check which gallon a number refers to before converting fuel, recipes, or oil quotes.

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

A US gallon is exactly 3.785411784 litres (= 231 cubic inches, traced to the 1706 Queen Anne wine gallon and adopted as the US standard in 1836). A UK (imperial) gallon is exactly 4.54609 litres (UK Weights and Measures Act 1985). The UK gallon is about 20% larger; equivalently, a US gallon is about 17% smaller (the two percentages are inverse, not equal). In numbers, 1 US gal ÷ 1 UK gal = 0.83267, so a US gallon is 83.27% of a UK gallon. They are not roundings of each other.

How many millilitres are in a US fluid ounce?

Exactly 29.5735295625 mL. The US fluid ounce is defined as 1/128 of a US gallon, so 3785.411784 mL ÷ 128 = 29.5735295625 mL. For kitchen work the 30 mL/oz shortcut is fine; US nutrition labels even use exactly 30 mL as a "common household" ounce per 21 CFR §101.9.

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.

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 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 the binding statutory value in force in the United Kingdom and several Commonwealth and 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 reduces to 1728/231). 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.

How many litres are in a cubic foot?

Exactly 28.316846592 litres (shown at auto-precision as 28.3168 L). A cubic foot is defined in NIST SP 811 Appendix B.8 as exactly 0.028316846592 m³ = 0.3048³ m³. Converted to US gallons that is 1728/231 = 7.480519480… US gal per ft³, a repeating rational.

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 shows whatever precision you ask for, up to 15 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.

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 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 from the wine gallon of 231 cubic inches. The UK 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 this volume converter free?

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

Sources & References

  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

Content verified by the Smart Calculators Team