Pressure Unit Converter

Convert between psi, bar, atm, Pascal, mmHg, and Torr pressure units with formula display.

Tested tool guide Tested browser tools Checked August 16, 2026

What Pressure Unit Converter does, with a checked example

Type a pressure in any of six common units - psi, bar, atmosphere, pascal, mmHg, or torr - and the tool returns the equivalent in all the others, with the conversion factor shown for each pair. Every unit reduces to the pascal (1 N/m2), the SI unit of pressure, through fixed definitions: a bar is exactly 100,000 Pa, a standard atmosphere exactly 101,325 Pa, a psi exactly 6,894.757... Pa. What surprises most users: mmHg and torr are not quite identical - they differ by about one part in seven million - so they agree at ordinary precision even though the formulas differ.

Worked example

A concrete input and expected output from the current implementation.

Input

1 atm

Expected output

101,325 Pa; 1.01325 bar; 14.696 psi; 760 mmHg; 760 torr

One standard atmosphere is defined as exactly 101,325 Pa. Dividing by 100,000 Pa per bar gives 1.01325 bar, and dividing by 6,894.757293168 Pa per psi gives 14.6959487755 psi, displayed as 14.696. By definition 1 atm equals exactly 760 mmHg and 760 torr.

How the result is produced

Pascal as the common base

Each unit has an exact, fixed value in pascals. The bar is defined as 100,000 Pa; the standard atmosphere as 101,325 Pa; the psi as 6,894.757293168 Pa, derived from the pound-force (4.4482216152605 N) divided by the square inch (0.0254 m) squared; and the conventional mmHg as 133.322387415 Pa. Entering a value converts it to pascals first, then to every other unit by dividing by that unit's factor.

Formula display and direction

For each target unit the tool shows the calculation as the entered value times a constant factor, so you can see which definition produced the number. Because every factor is fixed, conversions work in both directions: convert psi to bar and back and you recover the original digits, limited only by the decimals displayed. Mercury-column readings in mmHg vary with temperature and gravity; the converter uses the fixed conventional value.

Good uses

Checking tire or pump pressure against a foreign spec: a US gauge reads 32 psi while the tire sidewall says 2.2 bar, and the tool shows those are 2.206 bar and 31.9 psi respectively.
Converting a barometric reading for a record or spreadsheet: a station barometer shows 762 mmHg, which works out to 101,591.7 Pa (multiply by 133.322387415), just above the 101,325 Pa standard atmosphere.
Scuba tank fills: the gauge on an aluminum 80 tank reads 3,000 psi while the fill station and dive tables use bar, and 3,000 psi is 206.8 bar.

Limits and checks

Gauge versus absolute pressure. The tool converts the number you type as an absolute pressure. A tire gauge reads gauge pressure: 0 psi on the gauge is really about 14.7 psi (1 atm) absolute, so add one atmosphere before converting if you are doing gas-law math that needs absolute values.
mmHg and torr are separate definitions, not the same unit: torr is exactly 1/760 of an atmosphere (133.322368 Pa), while conventional mmHg is 133.322387415 Pa. They differ by about 0.000019 Pa, roughly one part in seven million, so the outputs look identical until the tool shows six or more decimals.
Result rounding. Displayed values are rounded to the tool's precision, so converting 14.696 psi to bar and back may show 14.696 or 14.6959 rather than the exact digits you entered. The underlying factors are exact; only the shown digits are rounded.

Common questions

Are mmHg and torr the same thing?

Not exactly. The torr is defined as exactly 1/760 of a standard atmosphere, or 133.322368 Pa, while the conventional millimetre of mercury is defined as 133.322387415 Pa. The gap is about 0.000019 Pa, a relative difference of 0.000015%. For blood pressure, weather, and vacuum work they are interchangeable; only metrology-grade comparisons care about the difference.

Why does 1 atm come out as 14.696 psi when I learned 14.7?

14.7 is the rounded shorthand. The exact value is 101,325 Pa divided by 6,894.757293168 Pa per psi, which is 14.6959487755 psi, or 14.696 rounded to three decimals. The extra digits matter when you add one atmosphere of offset to a gauge reading inside a calculation, so the tool keeps them.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.