PSI Converter
Unit ConversionConvert psi to pascals, kPa, MPa, bar, atmospheres, mmHg, inHg, ksi, kgf/cm² and inches of water. Type into any box and every other unit updates.
PSI
Metric
Atmosphere and Mercury
US and Engineering
1 PSI = 6,894.757293 Pascals ⟷ 1 Pascal = 0.000145038 PSI
1 PSI = 6.894757 Kilopascals ⟷ 1 Kilopascal = 0.145038 PSI
1 PSI = 0.00689476 Megapascals ⟷ 1 Megapascal = 145.037738 PSI
1 PSI = 0.0689476 Bar ⟷ 1 Bar = 14.503774 PSI
1 PSI = 0.068046 Atmospheres ⟷ 1 Atmosphere = 14.695949 PSI
1 PSI = 51.714925 mmHg ⟷ 1 mmHg = 0.0193368 PSI
1 PSI = 2.036021 Inches of Mercury (inHg) ⟷ 1 Inch of Mercury (inHg) = 0.491154 PSI
1 PSI = 0.001 KSI ⟷ 1 KSI = 1,000 PSI
1 PSI = 0.070307 kgf/cm² ⟷ 1 kgf/cm² = 14.223343 PSI
1 PSI = 27.707592 Inches of Water (60°F) ⟷ 1 Inch of Water (60°F) = 0.0360912 PSI
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Unit Conversion calculators
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SponsoredThis PSI converter shows a pressure in pounds per square inch next to pascals, kilopascals, megapascals, bar, atmospheres, millimeters and inches of mercury, ksi, kilograms-force per square centimeter and inches of water. Type into any box and the others update as you type.
PSI is the pressure of one pound of force on one square inch. Its size is fixed by three definitions, the avoirdupois pound, standard gravity and the inch, which make 1 psi about 6,894.757 pascals. It is the everyday pressure unit in the US for tires, air compressors and plumbing.
A gauge reads pressure above the surrounding air, so a negative psi reading is a partial vacuum. The converter accepts negative values down to a full vacuum, about -14.7 psi, and clears the other boxes below that. The section on PSIG and PSIA explains when to add the air pressure back.
What Is PSI
PSI stands for pounds per square inch, more precisely pounds-force per square inch. A pound-force is the weight of one avoirdupois pound (exactly 0.45359237 kg) under standard gravity (exactly 9.80665 m/s²), and an inch is exactly 0.0254 m. Dividing the force by the area gives 1 psi as a fraction with a repeating decimal, about 6,894.757293 pascals, which is why converters show it rounded. NIST SP 811 lists the factor.
Because psi is built on a force, a pressure in psi converts to newtons per square meter through the pound-force, and the Pound-Force to Newtons Converter shows that step on its own.
PSI and KSI
A kip is 1,000 pounds of force, so 1 ksi is exactly 1,000 psi. Engineers use ksi for material strength and stress, where values in psi would run to many digits.
PSIG vs PSIA
Gauge pressure (psig) is measured from the air around the gauge, so a tire gauge reads 0 before it touches the valve. Absolute pressure (psia) is measured from a perfect vacuum. The two differ by the local air pressure, about 14.7 psi at sea level in standard conditions.
- Start with the gauge reading in psig, for example 30 psig.
- Add the local air pressure. At the standard atmosphere that is about 14.6959 psi.
- 30 psig is then about 44.696 psia.
Changing the unit does not change the reference: 30 psig converts to about 206.84 kPa gauge, not absolute. Real air pressure changes with the weather and with height above sea level, so for careful work use the local barometer reading instead of 14.7. The Compression Ratio to PSI Calculator asks for the local atmospheric pressure in psi for the same reason.
Gauge Pressure Formula
The equation for gauge pressure is: gauge pressure = absolute pressure − atmospheric pressure. Rearranged, absolute pressure = gauge pressure + atmospheric pressure. Both sides must use the same unit, so convert first if the readings are in different units.
Can Pressure Be Negative
Absolute pressure cannot be negative; zero is a perfect vacuum. Gauge pressure can be: a reading below the surrounding air, such as a vacuum pump or the suction side of a system, shows as a negative number. The lowest possible gauge reading is minus the local air pressure, about -14.7 psi at sea level. A differential pressure gauge reads the difference between two points in a system, such as across a filter, and that difference converts between units the same way.
Tire Pressure in PSI, Bar and kPa
NHTSA advises checking tire pressure cold, before driving or after the car has been parked for at least three hours, against the recommended pressure on the label on the driver's door edge or door post, or in the owner's manual. That figure is given in psi and sometimes in kPa. The number molded into the tire sidewall is the maximum pressure, not the recommended one. The chart converts common tire (tyre) pressures between psi, bar and kPa, rounded.
| PSI | Bar | Kilopascals |
|---|---|---|
| 26 psi | 1.79 bar | 179.3 kPa |
| 28 psi | 1.93 bar | 193.1 kPa |
| 30 psi | 2.07 bar | 206.8 kPa |
| 32 psi | 2.21 bar | 220.6 kPa |
| 33 psi | 2.28 bar | 227.5 kPa |
| 35 psi | 2.41 bar | 241.3 kPa |
| 36 psi | 2.48 bar | 248.2 kPa |
| 38 psi | 2.62 bar | 262 kPa |
| 40 psi | 2.76 bar | 275.8 kPa |
| 44 psi | 3.03 bar | 303.4 kPa |
Going the other way, 2.2 bar is about 31.9 psi and 2.5 bar is about 36.3 psi. Tire size, not pressure, sets the diameter and revolutions per mile, which the Tire Size Calculator works out.
PSI Conversions
Single conversions that start from or end in this page's units, one page per pair.
- Bar to PSI Converter: 1 bar is about 14.503774 psi
- Bar to PSIG Converter: for gauge readings, 1 bar is about 14.503774 psi
- Kilopascals to PSI Converter: 1 kilopascal is about 0.145038 psi
- Megapascals to PSI Converter: 1 megapascal is about 145.037738 psi
- Megapascals to PSIG Converter: for gauge readings, 1 megapascal is about 145.037738 psi
- KSI to PSI Converter: 1 ksi equals exactly 1,000 psi
- Pascals to PSI Converter: 1 pascal is about 0.000145038 psi
- PSI to Atmospheres Converter: 1 psi is about 0.068046 standard atmospheres
- PSIG to PSIA Converter: adds the standard atmosphere, about 14.6959 psi, to a gauge reading
- kgf/cm² to PSI Converter: 1 kilogram-force per square centimeter is about 14.223343 psi
- PSI to Inches of Water Converter: 1 psi is about 27.707592 inches of water
Other Pressure Converters
Each converter below shows one pressure in many units at once, starting from a different unit.
- Pressure Unit Converter: one pressure in every common unit at once
- Kilopascal Converter: kilopascals to psi, bar, atm, hPa and more
- Megapascal Converter: megapascals to psi, ksi, bar, GPa and more
- Pascal Converter: pascals to hPa, kPa, MPa, GPa, psi and more
- Atmosphere Converter: standard atmospheres to psi, kPa, torr, mmHg and more
- Barometric Pressure Converter: inches of mercury to hPa, millibars, mmHg and more
Frequently Asked Questions
How do I convert psi to bar?
Divide psi by about 14.5038, or multiply by about 0.0689476. For example, 32 psi is about 2.206 bar.
How many psi is 1 atmosphere?
One standard atmosphere is about 14.6959 psi, usually rounded to 14.7 psi. One standard atmosphere is exactly 101,325 pascals, while the psi is a number of pascals with a repeating decimal, so the result has a long decimal.
Is PSI the same as PSIG?
On tire, compressor and plumbing gauges, a plain psi reading is a gauge reading, so it means psig. When absolute pressure is meant, it is written psia. The size of one psi is the same in both; only the zero point differs.
How many kPa is 1 psi?
1 psi is about 6.8948 kPa. Multiply psi by about 6.895 to get kilopascals.
Why does the converter stop at about -14.7 psi?
A negative psi value is a gauge reading below the surrounding air. A perfect vacuum is the lowest pressure possible, which is about -14.7 psi on a gauge at standard sea-level air pressure, so values below that clear the other boxes.
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