Pressure Converter
PSI · Bar · Pascal · Atm · mmHg · Torr
Enter a pressure value and select units to convert.
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Pressure Quick Reference
1 psi = 6,894.757 Pa = 0.0689476 bar, so to convert psi to bar you multiply by 0.0689476: a 32 psi tire is 2.21 bar. One standard atmosphere is exactly 101,325 Pa and one bar exactly 100,000 Pa. Enter any value above and the converter shows it in all ten units, from pascals to inches of mercury.
Standard atmospheric pressure at sea level is 101,325 Pa = 1 atm = 1.01325 bar = 14.696 psi = 760 Torr. The pascal, atmosphere, bar and Torr figures are exact by definition; 14.696 psi is rounded from 14.69595.
| Reference Point | PSI | Bar | kPa |
|---|---|---|---|
| Standard atmosphere | 14.696 | 1.01325 | 101.325 |
| Car tyre (typical) | 32 to 35 | 2.2 to 2.4 | 220 to 241 |
| Blood pressure 120 mmHg (gauge) | 2.32 | 0.16 | 16.0 |
| Ocean at 1,000 m depth (approx., gauge) | 1,450 | 100 | 10,000 |
| Everest summit (8,848 m) | 4.9 | 0.34 | 33.7 |
Exact Pressure Conversion Factors
The pascal (one newton per square meter) is the SI unit. Every other unit is defined as a fixed number of pascals.
| Unit | Pascals | Definition |
|---|---|---|
| kilopascal (kPa) | 1,000 | Exact |
| hectopascal (hPa) = millibar | 100 | Exact |
| bar | 100,000 | Exact |
| standard atmosphere (atm) | 101,325 | Exact |
| psi (lbf/in²) | 6,894.757 | One pound force on one square inch: 0.45359237 kg × 9.80665 m/s² ÷ 0.0254² m² |
| Torr | 133.322368 | Exactly 1/760 of an atmosphere |
| mmHg | 133.322387 | Conventional millimeter of mercury (mercury at 0°C, standard gravity) |
| inHg | 3,386.389 | 25.4 conventional mmHg |
Pressure Conversion Matrix
Read across: one unit in the first column equals the values in that row.
| 1 unit | kPa | bar | atm | psi | mmHg | inHg |
|---|---|---|---|---|---|---|
| kPa | 1 | 0.01 | 0.00986923 | 0.145038 | 7.50062 | 0.295300 |
| bar | 100 | 1 | 0.986923 | 14.5038 | 750.062 | 29.5300 |
| atm | 101.325 | 1.01325 | 1 | 14.6959 | 760.000 | 29.9213 |
| psi | 6.89476 | 0.0689476 | 0.0680460 | 1 | 51.7149 | 2.03602 |
| mmHg | 0.133322 | 0.00133322 | 0.00131579 | 0.0193368 | 1 | 0.0393701 |
| inHg | 3.38639 | 0.0338639 | 0.0334211 | 0.491154 | 25.4 | 1 |
Tire Pressure: psi to bar and kPa
Tire gauges read gauge pressure (above the surrounding air). Car door placards in the US list psi; European cars and many pumps use bar or kPa.
| psi | bar | kPa | Typical use |
|---|---|---|---|
| 28 | 1.93 | 193 | Small cars, light loads |
| 30 | 2.07 | 207 | Passenger cars |
| 32 | 2.21 | 221 | Passenger cars |
| 35 | 2.41 | 241 | Passenger cars, SUVs |
| 40 | 2.76 | 276 | Loaded SUVs, some pickups |
| 44 | 3.03 | 303 | Common maximum on passenger tire sidewalls |
| 50 | 3.45 | 345 | Light truck tires |
| 80 | 5.52 | 552 | Road bike tires |
| 100 | 6.89 | 689 | Road bike tires, high end |
Always inflate to the number on the driver's door placard, not the maximum printed on the tire.
Gauge vs Absolute and Other Common Mistakes
- Gauge vs absolute. A tire at 32 psi gauge (psig) holds 46.7 psi absolute (psia), because the air around it already presses at 14.7 psi. Add one atmosphere to go from gauge to absolute.
- bar vs atm. They are close but not equal: 1 atm = 1.01325 bar. Swapping them causes a 1.3% error.
- mmHg vs Torr. They differ by less than one part in 7 million, so for blood pressure or vacuum work you can treat them as equal. The converter still keeps them apart.
- inHg in weather reports. US forecasts and altimeter settings use inches of mercury. Standard sea-level pressure is 29.92 inHg = 1,013.2 hPa.
- Blood pressure. 120/80 mmHg is 16.0/10.7 kPa. It is a gauge reading above atmospheric pressure.
Method and sources. Factors from NIST Special Publication 811 (Appendix B): standard atmosphere 101,325 Pa, bar 100,000 Pa, psi 6,894.757 Pa, conventional millimeter of mercury 133.3224 Pa, inch of mercury 3,386.389 Pa, torr 101,325/760 Pa. The psi value follows from the exact pound (0.45359237 kg), standard gravity (9.80665 m/s²) and inch (0.0254 m). Every value in the tables was computed from these factors.
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Pressure Questions
Multiply PSI by 0.0689476 to get bar. Example: 30 PSI = 2.07 bar. To go the other way, multiply bar by 14.5038. Car tyres are typically 30 to 35 PSI (2.07 to 2.41 bar). Bicycle tyres range from 80 to 120 PSI (5.5 to 8.3 bar) for road bikes.
Standard atmosphere (atm) = 14.696 PSI = 1.01325 bar = 101,325 Pa = 760 mmHg. It represents average sea-level air pressure. Note: 1 bar is not exactly 1 atm, they differ by about 1.3%. Meteorologists use millibar (mbar) or hectopascal (hPa): 1 bar = 1,000 mbar = 1,000 hPa.
PSI (pounds per square inch) is used in the US and UK for tyres, hydraulics and gas. kPa (kilopascal) is the SI metric unit: 1 PSI = 6.89476 kPa. Tyre pressure in Europe is shown in bar or kPa. A typical car tyre at 32 PSI = 220.6 kPa = 2.21 bar.
mmHg (millimeters of mercury) is used in medicine for blood pressure and in meteorology. 1 mmHg = 133.322 Pa = 0.0193368 PSI. Normal blood pressure is 120/80 mmHg. 1 mmHg equals 1 torr to within one part in 7 million (the torr is exactly 1/760 of an atmosphere). The torr is named after Evangelista Torricelli, inventor of the barometer.
1 bar = 100,000 Pa = 100 kPa. The pascal is the SI unit of pressure (1 N/m²). Standard atmospheric pressure is 101,325 Pa = 1.01325 bar. In engineering: 1 MPa = 10 bar = 145.04 PSI, used for concrete strength and high-pressure hydraulics.
Vacuum is pressure below atmospheric. Perfect vacuum = 0 Pa absolute. Gauge pressure measures relative to atmosphere. A household vacuum cleaner creates about −20 kPa gauge (−2.9 PSI). Industrial vacuum systems reach −99 kPa gauge. Medical suction is typically −40 to −80 kPa gauge.
Pressure drops roughly 12 Pa per meter at sea level, following an exponential curve. At 5,500 m altitude, pressure is about half sea-level (50 kPa). At Everest summit (8,848 m): ~33.7 kPa = 4.9 PSI = 0.33 atm. Commercial aircraft cabins are pressurised to about 75 kPa (equivalent ~2,400 m).
Scuba tanks are filled to 200 to 300 bar (2,900 to 4,350 PSI). Ambient water pressure increases by 1 bar per 10 meters depth. At 30 m: 4 bar absolute. This is why divers must not hold their breath while ascending: expanding gas can cause lung over-expansion injury.
Absolute pressure is measured from perfect vacuum. Gauge pressure is relative to local atmospheric pressure. A car tyre at 32 PSI gauge = 46.7 PSI absolute. Most everyday measurements (tyres, blood pressure, gas lines) use gauge pressure. Scientific measurements use absolute.
Meteorologists use hectopascal (hPa), equal to millibar. Standard sea-level pressure = 1,013.25 hPa. Low pressure (storms): below 1,000 hPa. High pressure (fair weather): above 1,020 hPa. The lowest central pressure measured in an Atlantic hurricane was 882 hPa (Wilma, 2005).
29.92 inHg = 1,013.2 hPa, which is the same number in millibars. It is standard sea-level pressure, the reference setting for aircraft altimeters in the US. Each inch of mercury is 33.864 hPa, so 30.00 inHg is 1,015.9 hPa and 29.50 inHg is 999.0 hPa.
Multiply kPa by 0.145038. 220 kPa is 31.9 psi, 250 kPa is 36.3 psi and 1 MPa (1,000 kPa) is 145.04 psi. To go from psi to kPa, multiply by 6.89476.