Pressure Converter
Convert between SI, atmospheric, and gravitational pressure units (pascal, kilopascal, megapascal, bar, millibar, atmosphere, torr, mmHg, psi, kgf/cm², inH2O, cmH2O) with NIST-grade exact factors and conventional liquid-column values.
psi
Result
0.0689476 bar
1 psi= 0.068948 bar
Auto
All units
| Unit | Value |
|---|---|
| Pascal (Pa) | 6,894.76 |
| Kilopascal (kPa) | 6.89476 |
| Megapascal (MPa) | 0.00689476 |
| Bar (bar) | 0.0689476 |
| Millibar (mbar) | 68.9476 |
| Standard atmosphere (atm) | 0.068046 |
| Torr (Torr) | 51.7149 |
| Millimeter of mercury (mmHg) (mmHg) | 51.7149 |
| Pound per square inch (psi) (psi) | 1 |
| Kilogram-force per square centimeter (kgf/cm²) | 0.070307 |
| Centimeter of water (cmH₂O) (cmH₂O) | 70.307 |
| Inch of water (inH₂O) (inH₂O) | 27.6799 |
Pressure converter: psi, bar, kPa, atm, mmHg and more.
Enter a value in psi, bar, kPa, atm, torr or mmHg and this converter returns it in every other pressure unit, routing through the pascal. The unit it earns its keep on is the atmosphere: 1 atm is 14.6959 psi or 101.325 kPa, close to 1 bar but not the same.
What Is a Pressure Converter?
One atmosphere of ordinary air reads as 14.6959 psi on a US gauge, 101.325 kPa on an SI datasheet, 760 torr in a vacuum lab, and roughly 1013 mbar on tonight's weather map. Same push of air, four numbers that share no unit — which is exactly the mess a pressure converter cleans up.
Pressure is force spread over an area, and almost every field that measures it invented its own scale. The sticker in a car door jamb lists tires in psi; the European manual for the same car says bar; a barometer talks hPa; the cuff at a checkup reads mmHg; a CPAP machine is set in cmH₂O; a diver counts bar by depth. To move a reading from any one of those worlds into another, this tool sends it through a single base unit — the pascal (Pa), where 1 Pa is one newton spread over one square metre — and reads it back out wherever you need it.
The units sort into a few families. The SI scale runs pascal, kilopascal and megapascal. The atmospheric group holds the bar, the millibar (identical to the hectopascal weather forecasters use), and the standard atmosphere. The imperial world uses the pound per square inch. The liquid-column units survive where a mercury or water manometer once ruled: torr and mmHg in medicine and vacuum work, cmH₂O and inH₂O in breathing equipment and low-pressure HVAC. And the older technical unit, the kilogram-force per square centimetre, still fills gauges and boiler plates across Japan, India, Brazil and any workshop with pre-1980 machinery. The everyday anchors people actually search for drop straight out: 1 bar is 14.5038 psi, 1 psi is 6894.76 Pa, and one standard atmosphere is 101.325 kPa.
Two distinctions are worth carrying in your head. First, an atmosphere and a bar are neighbours, not twins — 101,325 Pa versus 100,000 Pa, about 1.3% apart — which is why IUPAC in 1982 quietly redefined chemistry's "standard pressure" from 1 atm down to exactly 1 bar, to kill the awkward 1.01325 factor. A spec that just says "atm" is therefore not interchangeable with one that says "bar." Second, every reading is either gauge (measured above the surrounding air) or absolute (measured from a vacuum), and the two sit about one atmosphere apart. This converter changes the unit; it does not add or remove that atmosphere, so a gauge number stays gauge and an absolute number stays absolute.
How to Use the Pressure Converter
Choose your starting unit in the From menu, choose the unit you want in the To menu, and type the number — the result appears as you type and updates on every keystroke. Tap the result to copy it. Both menus carry the full unit list, so no pairing is baked in: psi to bar, kPa to psi, bar to atm, MPa to psi or mmHg to kPa all work the same way, and the precision control lets you pin the number of decimals when a result runs long.
By hand it is two steps, because every unit is pinned to the pascal. Multiply your value by its pascal factor to reach pascals, then divide by the target unit's factor. Take a 35 psi tire into kilopascals: 35 × 6894.76 gives 241,317 Pa, which is 241.3 kPa (and dividing instead by 100,000 lands on 2.41 bar). Going the other way for a US gauge, 250 kPa is 250,000 Pa, and 250,000 ÷ 6894.76 comes out to about 36.3 psi. The same two moves handle every unit in the list — only the two factors change.
The Pressure Conversion Formula
- = The pressure you start from, in the source unit
- = Pascals in one source unit — its factor to the pascal (6894.757293 for psi, 101325 for atm, 100000 for bar)
- = Pascals in one target unit — its factor to the pascal
- = The converted pressure, in the target unit
Every pressure conversion is a single multiplication, because all pressure units share the same zero: zero of anything is zero pascals. Give each unit one number — how many pascals it equals — and any pair of units is two scalings apart. Scale the input up to pascals with the source factor, then scale back down with the target factor. There is no offset to add, which is why psi to bar converts the same clean way as mmHg to kPa.
That missing offset is also the reason this tool does not touch the gauge-versus-absolute question. Converting a gauge reading into an absolute one is not a unit change at all — it means adding one atmosphere (about 14.6959 psi, or 101.325 kPa), a shift the pure-ratio formula above never applies. Feed it 32 psi gauge and it returns the same pressure in other units, still gauge; if you need absolute, add the atmosphere yourself first.
Most of the factors are exact definitions. The SI units step by powers of ten (1 kPa = 1000 Pa, 1 MPa = 1,000,000 Pa); the bar is exactly 100,000 Pa and the millibar exactly 100 Pa; the standard atmosphere is exactly 101,325 Pa; the pound per square inch works out to 4.4482216152605 N ÷ 0.0254² m² = 6894.757293 Pa exact; and the technical kgf/cm² is exactly 98,066.5 Pa. Four units are the exceptions, tagged non-exact because they rest on a division or a density convention: the torr is 101,325 ÷ 760 = 133.32236842 Pa (a quotient that never terminates), the millimetre of mercury is the NIST conventional 133.322387415 Pa, the centimetre of water is 98.0665 Pa and the inch of water 249.0889 Pa. Everything you see rounded — 1 bar as 14.5038 psi, 1 atm as 14.6959 psi — is the tidy face of one of those exact ratios, and raising the precision brings the hidden digits back.
Common Pressure Conversions
| Conversion | Result | Exact? |
|---|---|---|
| 1 standard atmosphere (atm) | 101.325 kPa | exact |
| 1 standard atmosphere (atm) | 1.01325 bar | exact |
| 1 standard atmosphere (atm) | 14.6959 psi | rounded |
| 1 standard atmosphere (atm) | 760 torr | exact |
| 1 bar | 100 kPa | exact |
| 1 bar | 14.5038 psi | rounded |
| 1 bar | 0.986923 atm | rounded |
| 1 psi | 6.89476 kPa | rounded |
| 1 kPa | 0.145038 psi | rounded |
| 1 MPa | 145.038 psi | rounded |
| 1 kgf/cm² | 98.0665 kPa | exact |
| 1 kgf/cm² | 14.2233 psi | rounded |
| 1 mmHg | 133.322 Pa | non-exact |
| 1 inch of water (inH₂O) | 249.089 Pa | non-exact |
Worked Pressure Conversions
Car tire: 35 psi in kPa and bar
A US door-jamb sticker reading 35 psi is 241.3 kPa or 2.41 bar. Multiply psi by 6894.76 to reach pascals — 35 × 6894.76 = 241,317 Pa — then divide by 1000 for kilopascals (241.3 kPa) or by 100,000 for bar (2.41 bar). Reverse it for an SI dashboard readout: 240 kPa is 240,000 ÷ 6894.76 = 34.8 psi. Passenger cars typically run 32–35 psi cold, which is why the 220–250 kPa band and the 2.2–2.4 bar band all describe the same handful of tires.
European spec: 2.4 bar in psi
A manual that lists the rear tire at 2.4 bar wants 34.8 psi on a US gauge. Multiply bar by 14.5038: 2.4 × 14.5038 = 34.8 psi, and the same 2.4 bar is 240 kPa. Going back the other way, a 33 psi reading is 33 × 0.0689476 = 2.28 bar. The gap between bar and psi is a factor of about 14.5, so a European "2.4" and an American "35" are close cousins — mistake one scale for the other and you would inflate a tire to roughly 14 times its target.
Sealed spec: 2 atm in kPa, and why it is not 2 bar
A component rated for 2 atm holds 202.65 kPa — multiply atmospheres by 101.325. Read that same "2" as 2 bar and you would design for 200 kPa, short by 2.65 kPa, because one atmosphere is 101.325 kPa while one bar is only 100 kPa. The 1.3% gap is invisible on a bike pump and decisive on a calibration certificate. For reference, that single atmosphere is also 14.6959 psi and exactly 760 torr, the anchor every other pressure unit is measured against.
Blood pressure: 120/80 mmHg in kPa
A cuff reading of 120/80 mmHg is 16.0/10.7 kPa. Multiply each mmHg figure by 0.133322: 120 × 0.133322 = 16.0 kPa and 80 × 0.133322 = 10.7 kPa. Some European charts and ventilator displays use kPa, so this is the conversion that lines a home monitor up with a hospital screen. Because 1 mmHg and 1 torr agree to within about a millionth, 120 mmHg is also 120 torr for any clinical purpose. Note the reading is gauge — pressure above the surrounding air — which is what a blood-pressure cuff measures.
Hydraulics and boilers: 20 MPa in psi and kgf/cm²
A hydraulic circuit specified at 20 MPa runs at 2901 psi. Multiply megapascals by 145.038: 20 × 145.038 = 2900.8 psi, which is also exactly 200 bar. On an older Asian-market gauge the same pressure reads 20,000 kPa ÷ 98.0665 = 203.9 kgf/cm². This is why engineers like MPa for hydraulics: a 3000 psi system collapses to a tidy 20.68 MPa (3000 ÷ 145.038), turning four-digit psi numbers into clean two-digit ones. One kgf/cm² is 0.980665 bar — close to a bar, but, like the atmosphere, deliberately not equal.
Common Pressure Conversion Mistakes
- Treating an atmosphere and a bar as the same unit. One standard atmosphere is 101,325 Pa; one bar is exactly 100,000 Pa — about 1.3% apart. They drifted together because IUPAC once set chemistry's standard pressure at 1 atm, then in 1982 moved it to exactly 1 bar to lose the messy 1.01325 factor. Casual talk can ignore the gap; a calibration report, a scuba table or a weather-model boundary cannot, so convert rather than assume when a datasheet just says "atm."
- Assuming torr and mmHg are two names for one unit. Both land within a whisker of 133.32 Pa, so blood-pressure and everyday vacuum readings swap freely between them — the two agree to better than one part in seven million. They are defined differently, though: a torr is exactly 1/760 of an atmosphere, while the mmHg is the NIST conventional 133.322387415 Pa. Treat them as equal for anything clinical, and mind the hair-fine gap only in primary vacuum metrology.
- Forgetting that a reading is gauge, not absolute. A tire at 32 psi means 32 psi above the surrounding air (gauge, or psig), not 32 psi measured from a vacuum (absolute, or psia). At sea level that same tire is about 46.7 psi absolute, because the air already contributes 14.6959 psi. This converter does pure unit math and never adds or subtracts that atmosphere, so if you need absolute pressure, add roughly 14.7 psi (or 101.325 kPa) yourself before converting.
- Ignoring the psia / psig — or bara / barg — suffix on a spec. The trailing letter is not decoration: "a" means absolute, "g" means gauge. A compressor rated 100 psig delivers 100 psi above atmosphere, but a vacuum spec of 5 psia is an absolute figure near a fifth of an atmosphere. Convert the number by all means, but carry its suffix across — dropping the a or g is how a gauge value silently gets read as absolute, throwing every downstream figure off by one atmosphere.
- Slipping a factor of 100 between bar, kPa and Pa. One bar is 100,000 Pa, 100 kPa and 1000 millibar, so it is easy to land a power of ten or two off: writing 2 bar as 200 Pa instead of 200,000 Pa, or reading a 1013 mbar barometer as 1013 Pa. Fix the prefix before you compare — kilo is ×1000, mega is ×1,000,000 — and double-check that a lone "2.2" on a tire chart is bar, not kPa, because the two differ by a factor of a hundred.
- Mixing several units inside one calculation. psi, bar, kPa and mmHg sit on wildly different scales — 1 bar is 100 kPa, 14.5038 psi and 750 mmHg — so adding or comparing raw numbers across units is meaningless. Convert every figure into a single unit first, then do the arithmetic, and only convert the final answer back out if the audience needs a different scale.
Pressure Converter — Frequently Asked Questions
How do I convert psi to bar?
Multiply the psi value by 6894.76 to get pascals, then divide by 100,000 — or just multiply psi by 0.0689476. So 1 psi is 0.0689476 bar, and a 32 psi tire is about 2.21 bar. Reading the other direction, 1 bar is 14.5038 psi.
How do I convert kPa to psi?
Divide the kPa figure by 6.89476, or multiply it by 0.145038. So 100 kPa is 14.5038 psi and 250 kPa is about 36.3 psi. Kilopascals turn up on SI-standard datasheets; psi on US gauges.
Is 1 atm the same as 1 bar?
No. One standard atmosphere is 101,325 Pa; one bar is exactly 100,000 Pa. The atmosphere is about 1.3% higher — 1 atm is 1.01325 bar and 1 bar is 0.986923 atm — so they are close neighbours but not equal.
How many pascals are in one atmosphere?
Exactly 101,325 Pa, which is 101.325 kPa. The same atmosphere is also 14.6959 psi, 760 torr, and 1.01325 bar.
Which is bigger, psi or bar?
The bar is far bigger: 1 bar equals 14.5038 psi, so it takes about 14.5 psi to match a single bar. That is why a European tire quoted as 2.4 bar reads 34.8 psi on a US gauge — the numbers look different but the pressure is the same.
What is torr, and where is it used?
One torr is 1/760 of a standard atmosphere, or 133.322 Pa, so 760 torr is exactly 1 atm. It is the working unit of vacuum technology and lab science, where low pressures are quoted in torr or millitorr rather than in tiny fractions of a pascal.
What is the difference between torr and mmHg?
Almost nothing in practice — both sit at about 133.32 Pa and agree to within one part in seven million. A torr is defined as 1/760 atm; the mmHg is fixed at 133.322387415 Pa. The gap only matters in precision vacuum metrology; for blood pressure they are interchangeable.
How do I convert mmHg to kPa for blood pressure?
Multiply the mmHg value by 0.133322. So a 120/80 mmHg reading is 16.0/10.7 kPa, and 140 mmHg is about 18.7 kPa. Some European monitors and ventilators display kPa, so this is the conversion that reconciles a home cuff with a hospital screen.
How many psi is 1 MPa?
One megapascal is 145.038 psi, and it is also exactly 10 bar. Hydraulic and structural specs favour MPa because it turns four-digit psi figures into tidy ones — a 3000 psi system is just 20.68 MPa (3000 ÷ 145.038).
How much pressure is in a car tire?
Most passenger cars run 32–35 psi cold, which is roughly 2.2–2.4 bar or 220–240 kPa. The exact target is on the door-jamb sticker, often printed in all three units. Tire specs are gauge pressure — measured above the surrounding air, not from a vacuum.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to the surrounding air; absolute pressure is measured from a perfect vacuum. A tire at 32 psi gauge is about 46.7 psi absolute at sea level, because the air already adds 14.6959 psi. Sensors label these psig, psia, barg and bara.
Does this converter switch between gauge and absolute pressure?
No — it only changes units. Converting gauge to absolute means adding one atmosphere (about 14.6959 psi or 101.325 kPa), which is not a unit change, so the tool never applies it. A gauge value stays gauge; add the atmosphere yourself first if you need absolute.
Is this pressure converter free?
Yes — no account and no install, and it runs entirely in your browser. Every pressure unit lives on one page, from Pa, kPa and MPa to bar, atm, psi, mmHg, torr, kgf/cm² and water-column units, so a weather chart, a tire spec and a datasheet all meet in one place.
How accurate is this pressure converter?
It uses the standard defined factors — 1 atm at 101,325 Pa, 1 bar at 100,000 Pa, 1 psi at 6894.757293 Pa — so the SI, bar, atm, psi and kgf/cm² values are fixed by definition. Only torr, mmHg and the water-column units rest on a division or density convention, so any small differences trace back to the display precision you pick.
Can I embed this pressure converter on my site?
Yes. An ad-free embeddable version is available, so engineering blogs, HVAC and dive-training sites, weather-hobby pages and physics-teaching material can drop the converter in without loading third-party trackers.
출처 및 참고문헌
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically (pressure section: standard atmosphere 101 325 Pa exact, kgf/cm² 98 066.5 Pa exact, psi 6 894.757 Pa as rounded NIST printing of the exact IEEE-754 product 6 894.757293168361 Pa, mmHg 133.322 387 415 Pa conventional)
- NIST Guide to the SI, Appendix B — Conversion factors (landing page with the canonical bold-is-exact convention used across pressure, force, length and torque units)
- BIPM — The International System of Units (SI Brochure, 9th edition 2019): the pascal (1 Pa ≡ 1 N/m²) is the SI derived unit of pressure; the bar (= 10⁵ Pa exact) and the millimetre of mercury are listed as non-SI units accepted for use with the SI in specific application domains
- BIPM — Resolution of the 3rd CGPM (1901): declaration that standard gravity g_n = 9.80665 m/s² exact, the upstream constant that anchors every gravitational pressure unit (kgf/cm² = 98 066.5 Pa exact, cmH₂O = 98.0665 Pa conventional, inH₂O = 249.0889 Pa conventional, mmHg = 133.322 387 415 Pa conventional)
- ISO 2533:1975 — Standard Atmosphere: fixes sea-level reference pressure at exactly 101 325 Pa, sea-level reference temperature at 288.15 K, and the lapse-rate / pressure-altitude profile used in aviation, ballistics and aerospace engineering. The downstream definitions of 1 atm = 1.01325 bar = 1 013.25 hPa = 760 Torr all flow from this document
- Wikipedia — Pascal (unit): SI derived unit of pressure equal to 1 N/m²; covers the relationship with the hectopascal (hPa = mbar) for meteorology and the kilopascal/megapascal multiples used in engineering (Wikidata Q44395)
- Wikipedia — Bar (unit): non-SI unit of pressure equal to exactly 100 000 Pa = 10⁵ Pa; widely used in meteorology, oceanography (1 bar ≈ 10 m seawater depth) and process engineering; the millibar (mbar) is numerically identical to the hectopascal (hPa) (Wikidata Q103510)
- Wikipedia — Pound per square inch: US customary unit of pressure equal to exactly 6 894.757293168361 Pa, the IEEE-754 product of the IYP-1959 inch (0.0254 m exact) and the CGPM-1901 pound-force (4.4482216152605 N exact); explains psig vs psia vs psid variants used on US industrial sensors (Wikidata Q626299)
- Wikipedia — Torr: non-SI unit of pressure defined as exactly 1/760 of a standard atmosphere = 101 325/760 ≈ 133.3223684 Pa; named after Evangelista Torricelli (1644 mercury barometer); explains the < 0.000015 % gap versus mmHg (the two units are interchangeable in clinical work but distinct in vacuum metrology) (Wikidata Q185648)
- Wikipedia — Standard atmosphere (unit): atm = exactly 101 325 Pa (10th CGPM 1954, codified in ISO 2533:1975); equivalent to exactly 760 Torr, exactly 1.01325 bar, exactly 1 013.25 hPa, and approximately 14.6959 psi — the anchor for every atmospheric pressure conversion (Wikidata Q177974)