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
- Pick the unit you are starting from in the From menu and type your value.
- Pick the unit you want in the To menu. The heading changes to match – for example “Standard Atmospheres to Pascals Converter”.
- The most common pressure units are shown below at the same time, so you can compare them at a glance.
- 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
Every pressure unit is defined by an exact factor relative to the pascal (the base unit). The calculator first turns the value you type into pascals, then turns that into the unit you picked in the “To” menu and into each of the common units below it. This two-step method means any unit can be converted to any other – 18 units are available in each menu – and you can type into any field, including a result, to work in the other direction. Changing a unit menu keeps the quantity the same and just re-expresses it, and the page heading and copied results follow your choice.
How to convert pressure units
- Choose the unit you have in the From menu and type the value, for example 1 atm.
- Choose the unit you want in the To menu, for example pascals. The page heading changes to “Standard Atmospheres to Pascals Converter”.
- 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
| Unit | Value |
|---|---|
| Pascals (Pa) | 101,325 |
| Kilopascals (kPa) | 101.325 |
| Bar (bar) | 1.01325 |
| Psi (psi) | 14.695949 |
| Millimetres of mercury (mmHg) | 759.99989 |
| Torr (Torr) | 760 |
| Inches of mercury (inHg) | 29.921252 |
Standard atmospheres conversion table
| Standard atmospheres | Pa | kPa | bar | psi |
|---|---|---|---|---|
| 0.5 | 50,662.5 | 50.6625 | 0.506625 | 7.3479744 |
| 1 | 101,325 | 101.325 | 1.01325 | 14.695949 |
| 2 | 202,650 | 202.65 | 2.0265 | 29.391898 |
| 3 | 303,975 | 303.975 | 3.03975 | 44.087846 |
| 5 | 506,625 | 506.625 | 5.06625 | 73.479744 |
| 10 | 1,013,250 | 1,013.25 | 10.1325 | 146.95949 |
What is a standard atmosphere?
The standard atmosphere is exactly 101,325 Pa, the average air pressure at sea level. Chemistry problems and diving depth calculations often use atm.
What is a pascal?
The pascal is the SI unit of pressure: one newton per square metre. It is small, so kilopascals and megapascals are used in practice.
What is a kilopascal?
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.
Common mistakes to avoid
Mixing gauge pressure (psig, barg) with absolute pressure (psia, bara), treating bar and atm as identical, and confusing kgf/cm² with bar.
Formula
1 atm = 101,325 Pa1 atm = 101.325 kPa1 atm = 1.01325 bar1 atm = 14.695949 psi1 atm = 759.99989 mmHgWorked example
Inputs — From: 1 atm.
Results — To = 101,325 Pa; Kilopascals = 101.325 kPa; Bar = 1.01325 bar; Psi = 14.69594878 psi; Millimetres of mercury = 759.99989173 mmHg; Torr = 760 Torr; Inches of mercury = 29.9212524 inHg.
Frequently asked questions
How many psi is 1 atm?
About 14.696 psi.
How many mmHg is 1 atm?
760 mmHg.
How much pressure at 10 m underwater?
About 2 atm absolute (1 from air, about 1 from water).
How do I change the units?
Pick any unit in the From and To menus. The value is converted in place, and the heading changes to show your conversion, for example “Standard Atmospheres to Pascals Converter”.
Can I type into any field?
Yes. Every field is editable, so you can start from whichever unit you have.
How many units can I convert between?
18 pressure units, from the everyday to the specialised.
Which units are exact?
All factors here are exact by definition except astronomical and similar reference values, which use internationally agreed constants.
What formula does the Atmosphere use?
1 atm = 101,325 Pa.