How to use the Pressure Converter
- Enter the pressure reading, for example 32 from a tire gauge.
- Choose the unit it is in and the unit you need.
- Read the result and the one-unit factor in both directions.
- Check the full list for every unit at once, and click any value to copy it.
Features
- Exact definitions for Pa, bar, atm, psi and torr
- Conventional mmHg, inHg and inches of water
- kgf/cm² (technical atmosphere) for older gauges
- hPa and mbar for weather maps
- Every unit at once with one-click copy
- Clickable table of everyday pressures
What pressure units measure
Pressure is force spread over an area. The SI unit, the pascal (Pa), is one newton per square meter, named after Blaise Pascal, who studied air pressure in the 17th century. A pascal is tiny, roughly the pressure of a sheet of paper lying on a table, so real-world values use kilopascals (kPa), megapascals (MPa) or hectopascals (hPa).
The family of units
- Bar is exactly 100,000 Pa, close to the air pressure at sea level. It is common for tires, scuba tanks and industrial equipment outside the US.
- Millibar and hectopascal are the same size (100 Pa). Weather maps use them: standard sea-level pressure is 1,013.25 hPa.
- Standard atmosphere (atm) is defined as exactly 101,325 Pa.
- psi, pounds-force per square inch, is the everyday US unit for tires, air compressors and plumbing. From the exact pound and inch it comes to 6,894.757 Pa.
- mmHg and torr come from the mercury barometer that Evangelista Torricelli built in the 1640s. The torr is exactly 1/760 of an atmosphere, and the conventional millimeter of mercury differs from it by less than one part in five million. Blood pressure is still recorded in mmHg.
- inHg is used for weather reports and aircraft altimeter settings in the US, where 29.92 inHg is standard pressure.
- kgf/cm², the technical atmosphere, is 98,066.5 Pa and still appears on older gauges in many countries.
Gauge versus absolute pressure
A tire gauge reads gauge pressure, the amount above the surrounding air. A tire at 32 psi on the gauge actually holds about 46.7 psi absolute at sea level. Engineers sometimes write psig and psia to make the difference clear. Convert like with like: this tool converts the number you give it and does not add or remove atmospheric pressure.
Worked examples
Car tire: 32 psi × 0.0689476 = 2.21 bar, or 220.6 kPa.
Weather: 1,013.25 hPa ÷ 33.8639 = 29.92 inHg.
Blood pressure: 120 mmHg × 0.133322 = 16.0 kPa.
Diving: every 10 m of seawater adds roughly 1 bar, so at 20 m you are near 3 bar absolute.
Reference table
| Unit | Pascals | psi |
|---|---|---|
| 1 kPa | 1,000 | 0.145038 |
| 1 bar | 100,000 | 14.5038 |
| 1 atm | 101,325 | 14.6959 |
| 1 kgf/cm² | 98,066.5 | 14.2233 |
| 1 mmHg | 133.322 | 0.0193368 |
| 1 inHg | 3,386.389 | 0.491154 |
Tips
Recommended tire pressures are printed on a label inside the driver’s door, often in both psi and kPa or bar. Pressure and temperature are linked: a tire loses roughly 1 psi for every 10 °F (about 5.6 °C) drop in air temperature, so check it when the tires are cold. The Temperature Converter helps when manuals mix scales.
Frequently asked questions
How many psi are in one bar?
One bar is about 14.5038 psi, and one psi is about 0.0689476 bar.
Is torr the same as mmHg?
Almost. One torr is exactly 1/760 of a standard atmosphere, and one conventional mmHg is 133.322387415 Pa. They differ by less than 0.00002%, so they are interchangeable in practice.
What is standard atmospheric pressure?
Exactly 101,325 Pa, which is 1,013.25 hPa, 1.01325 bar, about 14.696 psi, 760 mmHg or 29.92 inHg.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to the surrounding air, while absolute pressure is measured from a perfect vacuum. Absolute equals gauge plus atmospheric pressure.
Is kgf/cm² the same as bar?
Close but not equal. One kgf/cm² is 0.980665 bar, about 2% less.