What pressure units measure
Pressure is force spread over an area. The SI unit is the pascal (Pa), which is one newton per square meter. A pascal is very small, so kilopascals (kPa) and bars are common for everyday use. One kilopascal is 1,000 pascals, and one bar is 100,000 pascals.
Standard atmosphere (atm) is based on average air pressure at sea level and is defined as 101,325 pascals. PSI, pounds per square inch, is the customary unit in the US for tire pressure, compressed air and plumbing.
This converter works by turning your input into pascals and then dividing by the target unit's value in pascals. It covers five units: Pascal, Kilopascal, Bar, Atmosphere and PSI.
Where these conversions are useful
Tire pressure is the most familiar case. Cars sold in different markets show recommended pressure in PSI, bar or kPa, and gas station gauges may use another unit than your manual. Converting avoids guesswork when inflating.
Weather and altitude references often use kilopascals or atmospheres. Scuba and diving gear, pressure cookers, espresso machines and compressed air tools are often rated in bar or PSI. Engineers and technicians reading datasheets from different suppliers also need to compare values in a single unit.
Because a wrong pressure can matter for safety, it helps to double check the unit on the gauge or label before you read the number off. The conversion is only as reliable as the unit you select.
How to convert pressure with this tool
- Enter the value in the number box under From. It starts at 1.
- Choose your starting unit in the From drop-down: Pascal, Kilopascal, Bar, Atmosphere or PSI.
- Choose the target unit in the To drop-down from the same five.
- Read the result in the To box, which updates as you type or change a unit.
The default pair is Pascal to Kilopascal, so it starts with 0.001. Results are rounded to six decimal places. All maths is done in your browser.
Factors, examples and cautions
The factors used, in pascals, are: kilopascal 1000, bar 100,000, atmosphere 101,325 and PSI 6894.76. Worked checks: 1 atmosphere is 101,325 pascals and about 14.696 PSI, and 1 bar is 100 kilopascals. A tire reading of 32 PSI converts to about 2.206 bar.
Gauge pressure and absolute pressure are different. Most tire and compressed air gauges show gauge pressure, which is measured relative to the surrounding air, while some scientific values are absolute. This tool only converts units. It does not add or subtract atmospheric pressure, so it will not convert between those two kinds of reading.
The tool does not offer mmHg, inHg or torr. For readings in those units, convert via a published factor first. If you are working with other measurement types in the same project, the Energy Converter follows the same layout.