Atmosphere (atm) Converter

The standard atmosphere is defined as exactly 101,325 Pa, close to average sea-level air pressure. Chemists use it for gas-law problems and divers count about one extra atmosphere for every 10 m of seawater.

How to use the Atmosphere

1. Pick the unit you are starting from in the From menu and type your value.
2. Pick the unit you want in the To menu. The heading changes to match, for example “Standard Atmospheres to Pascals Converter”.
3. The most common pressure units are shown below at the same time, so you can compare them at a glance.
4. Type into any result to convert backwards, then use Copy results. The copied text starts with the heading for your chosen units.

Results update as you type. Everything is calculated in your browser.

How it works

Each of the 18 pressure units on this page is defined by an exact factor relative to the pascal, the base unit: 1 atm = 101,325 Pa and 1 kPa = 1,000 Pa, for example. The calculator first turns the value you type into pascals, then turns that into the unit you picked in the “To” menu and into kilopascals, bar and psi. Typing into any result works backwards the same way, so the standard atmospheres and pascals values always describe the same amount.

How to convert pressure units

1. Choose the unit you have in the From menu and type the value, for example 1 atm.
2. Choose the unit you want in the To menu, for example pascals. The page heading changes to “Standard Atmospheres to Pascals Converter”.
3. The calculator multiplies by the pascal factor of the “from” unit and divides by the factor of the “to” unit: 1 atm × 101,325 ÷ 1 = 101,325 Pa.

1 standard atmosphere in common units

Standard atmospheres conversion table

Pressure units explained

Standard atmosphere (atm)

The standard atmosphere is exactly 101,325 Pa, the average air pressure at sea level. Chemistry problems and diving depth calculations often use atm.

Pascal (Pa)

The pascal is the SI unit of pressure: one newton per square metre. It is small, so kilopascals and megapascals are used in practice.

Kilopascal (kPa)

A kilopascal is 1,000 Pa. Tyre pressures in Canada and Australia, weather data and boiler gauges often use kPa; standard air pressure is 101.325 kPa.

Bar (bar)

One bar is exactly 100,000 Pa, close to average atmospheric pressure. European tyre pressures, diving, espresso machines and industrial gauges use bar.

Pound per square inch (psi)

Pounds per square inch is the pressure of one pound-force on one square inch, about 6,895 Pa. U.S. tyre gauges, compressors and hydraulic equipment read psi.

Millimetre of mercury (mmHg)

Millimetres of mercury measure pressure by the height of a mercury column. Blood pressure is reported in mmHg, and 760 mmHg is one standard atmosphere.

Torr (Torr)

The torr is exactly 1/760 of a standard atmosphere, named after Evangelista Torricelli, inventor of the barometer. Vacuum systems are rated in torr.

Inch of mercury (inHg)

Inches of mercury are used for barometric pressure in U.S. weather reports and aviation altimeter settings; standard pressure is 29.92 inHg.