Pressure Converter

Pressure is force spread over an area, and the unit depends on the instrument: meteorologists read millibars, tyre gauges read psi, engineers use pascals or bar, and laboratories still quote atmospheres and Torr. A tyre set to 2.2 bar reads 31.91 psi on an American gauge, and the difference between gauge and absolute pressure is roughly one atmosphere. Convert once here and every scale agrees.

Enter values

Results

In pounds per square inch (psi): 14.5038
In kilopascals (kPa): 100
In millibars (mbar): 1,000
In atmospheres (atm): 0.986923
In torr: 750.0617
Exact factor: 1 bar = 14.503774 psi

How is the Pressure Converter calculated?

Enter the pressure, choose the unit printed on the gauge or datasheet, and choose the unit you want back. The headline result carries the answer while the rows beneath repeat the same pressure in pascals, kilopascals, bar, psi, atmospheres and Torr, so a unit slip is obvious. The last row states the exact factor — 1 bar = 14.503773773 psi — so the sum can be repeated on paper. Decimals are welcome and values run from zero to a billion.

Formula

Everything passes through pascals: pascals = value × from-unit factor, then target = pascals ÷ to-unit factor. Exact factors: 1 bar = 100,000 Pa · 1 mbar = 100 Pa · 1 kPa = 1,000 Pa · 1 MPa = 1,000,000 Pa · 1 atm = 101,325 Pa · 1 psi = 6,894.757293168 Pa · 1 Torr = 101,325 ÷ 760 Pa. One atmosphere is therefore exactly 760 Torr and 1,013.25 mbar.

Example

A tyre pressure of 2.2 bar is 2.2 × 14.503773773 = 31.91 psi, matching the 32 psi figure moulded into many sidewalls — and 32 psi converts back to 2.21 bar. In SI units that tyre sits at 220 kPa. Gauge readers add one twist: the atmosphere presses back with 14.7 psi, so 32 psi gauge is about 46.7 psi absolute. Standard atmosphere is the anchor: 101,325 Pa equals 1,013.25 mbar and 760 Torr exactly, which is why weather maps and vacuum pump specs quote the same air pressure two ways.

Things to remember

Pressure numbers mean little without their reference point and unit, so state both: bar or psi for tyres, pascals for engineering, Torr for vacuum work. Keep the exact factors — 1 atm = 101,325 Pa by definition — and gauge versus absolute stops being a source of surprises.

Frequently Asked Questions

What is the difference between gauge and absolute pressure?

Gauge pressure is measured against the air around you; absolute pressure is measured against a perfect vacuum. Standard air pressure is 101,325 Pa, about 14.7 psi or 1,013.25 mbar, so a tyre reading 32 psi on a gauge is roughly 46.7 psi absolute.

How many psi are there in one bar?

14.503773773 psi. Multiply bars by that figure, so 2.2 bar is 31.91 psi and 3 bar is 43.51 psi. Reverse it by dividing psi by 14.503773773, which makes 32 psi equal to 2.21 bar, or 220.63 kPa in SI units.

Is a torr the same as a millimetre of mercury?

Almost. The torr is exactly 101,325 ÷ 760 = 133.322368 Pa, while a millimetre of mercury is 133.322387415 Pa at standard gravity — a difference of about one part in ten million. Both round to 760 per atmosphere on any normal gauge.

Which pressure unit should I use for tyres?

Bar in most of the world and psi in the United States, with kilopascals common on European cars — 2.2 bar, 32 psi and 220 kPa all describe the same inflation. Check the placard in the door jamb, convert it here, and ignore the bar-or-psi argument on the forecourt.