Pressure Converter

How to convert pressure units

Enter a pressure, choose the unit you have, and choose the unit you want. All six units, Pa, kPa, bar, psi, atm and mmHg, update at once from a single entry.

The pascal is the internal base and every factor is exact, so bar to psi does not pass through a rounded intermediate. Remember that the tool converts units, not reference points: gauge and absolute pressure are the same number in different frames, and the offset is yours to apply.

• Type the pressure in the Value box, for example 32.
• Pick the From unit, for example Pound per square inch (psi).
• Pick the To unit, for example Bar.
• Read the result and check the kPa row, which is what most datasheets use.
• If you need absolute pressure from a gauge reading, add 1 atm (14.6959 psi or 101.325 kPa) after converting.

Gauge, absolute, and why the unit label is not enough

A pressure number carries two pieces of information: a magnitude and a reference point. Gauge pressure is measured relative to the surrounding atmosphere, which is what a tire gauge, a boiler gauge, and a blood pressure cuff all read. Absolute pressure is measured from a perfect vacuum. The same physical state is 32 psig or 46.7 psia, and the difference is one atmosphere.

This converter changes the magnitude and never touches the reference point. That is the correct behavior, because there is no way to guess from the number alone which frame it was measured in. If your source says psig, kPa gauge, or barg and your target needs absolute, add one atmosphere yourself: 14.6959487755 psi, 101.325 kPa, or 1.01325 bar.

• psig, barg, kPa(g): relative to atmosphere, what most gauges show.
• psia, bara, kPa(a): relative to vacuum, what thermodynamic tables use.
• Absolute equals gauge plus 1 atm at sea level, less at altitude.

Which pressure unit each field actually uses

Tires are the most common reason people land on a pressure converter, and they are split down the middle: US placards are in psi, European ones in bar, and Japanese service data often in kPa. Meteorology settled on hectopascals, which are numerically identical to the older millibar, so a 1013 hPa reading and a 1013 mbar reading are the same number.

Medicine kept mmHg for blood pressure and intraocular pressure, industrial process work runs on bar and kPa, and vacuum work drops into pascals and torr. The unit is a strong hint about the source of a figure, which is worth noticing when a spec sheet mixes two of them in the same table.