Result
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Facts and limits of this method
| Base unit | Pascal — all other units convert through it |
|---|---|
| 1 atmosphere | 101,325 Pa (standard atmospheric pressure at sea level) |
| 1 bar | 100,000 Pa (close to, but not equal to, 1 atmosphere) |
| 1 psi | ≈6894.757 Pa (pound-force per square inch) |
| 1 mmHg | ≈133.322 Pa (millimeter of mercury) |
| Total units | 8 — Pa, kPa, MPa, bar, atm, psi, mmHg, torr |
When it misleads you
- The calculation happens in two steps: the value is first converted to pascals, then from pascals to the target unit, so choosing the same unit for "from" and "to" leaves the result unchanged.
- Torr and millimeter of mercury were historically defined slightly differently (torr as 1/760 of a standard atmosphere, mmHg through the physical density of mercury and standard gravity), so their values differ at the sixth decimal place — negligible for most practical purposes.
- 1 atmosphere (101,325 Pa) is not equal to 1 bar (100,000 Pa) — these are close but distinct units, often confused when reading technical documentation.
- Rounding is applied only to the displayed result — internal calculations use the full precision of JavaScript floating-point numbers.
How it is calculated
Each of the eight units has a preset conversion factor to pascals — for example, 1 atmosphere = 101,325 Pa, 1 psi ≈ 6894.757 Pa.
The entered value is multiplied by the factor of the selected "from" unit, giving pressure in pascals.
The pressure in pascals is divided by the factor of the "to" unit, giving the result in the target unit.
The result is rounded to the chosen number of decimal places and updates instantly whenever the value, units or precision change.
Questions and answers
Are an atmosphere and a bar the same thing?
No, they're close but distinct units: 1 atmosphere = 101,325 Pa, while 1 bar = 100,000 Pa — a difference of about 1.3%.
What's the difference between a torr and a millimeter of mercury?
Historically they're independently defined units with very close values (differing at the sixth decimal place); for the vast majority of practical purposes they can be treated as interchangeable.
Where is psi used?
Pound-force per square inch is the standard pressure unit in the US, commonly seen on tire gauges, compressors and in technical documentation for American equipment.
Is my data sent anywhere?
No, the whole calculation runs in your browser.