Pressure Converter

How to use the pressure converter

1. Type a pressure in Value. A decimal point or a decimal comma both work, and negative values are accepted for gauge readings below atmospheric pressure.
2. Choose the starting unit in From and the target unit in To, for example bar and pound-force per square inch (psi).
3. The result appears as you type, with the full line below it (“1 bar ≈ 14.503774 psi”). Copy puts that line on your clipboard.
4. Swap units (⇄) reverses the conversion.
5. Significant figures sets the rounding. A “≈” sign means the displayed value has been rounded.

Below the result you get the pressure in every unit at once, a quick table for the selected pair, everyday references (tyres, blood pressure, an espresso machine, a scuba tank) and the value of each unit in pascals.

The definitions used

Every factor comes from an exact or conventional standard definition, never from a rounded approximation:

• Pascal (Pa): the SI unit, 1 newton per square metre. 1 hPa = 100 Pa, 1 kPa = 1,000 Pa, 1 MPa = 10⁶ Pa.
• Bar: exactly 100,000 Pa (1 mbar = 1 hPa = 100 Pa).
• Standard atmosphere (atm): exactly 101,325 Pa, fixed by the 10th General Conference on Weights and Measures (1954).
• psi (pound-force per square inch): 1 lbf ÷ 1 in². With the exact pound-force (4.4482216152605 N) and the exact inch (0.0254 m), 1 psi = 6,894.757293168… Pa.
• mmHg: the conventional millimetre of mercury, 133.322387415 Pa (a 1 mm column of mercury at a density of 13.5951 g/cm³ under standard gravity).
• Torr: exactly 1/760 atm, about 133.322368 Pa. It differs from the mmHg by less than one part in six million, so the two are interchangeable in practice, but this tool keeps them separate.
• inHg: 25.4 mmHg, about 3,386.39 Pa, used for weather and altimeter settings in North America.
• kgf/cm² (technical atmosphere): 98,066.5 Pa, still printed on some older gauges.

Gauge pressure and absolute pressure

A tyre gauge, a compressor or a pressure cooker shows gauge pressure: how much the pressure exceeds the surrounding air. Absolute pressure adds the atmosphere, about 1.013 bar (14.7 psi) at sea level. A tyre inflated to 2.3 bar gauge is therefore at about 3.3 bar absolute. In English, psig and psia mark the difference.

The conversion factor is the same in both cases, so this tool converts gauge values to gauge values and absolute values to absolute values. Just don’t mix the two.

Useful equivalents

• 1 bar ≈ 14.5038 psi ≈ 0.98692 atm
• 1 atm = 1.01325 bar ≈ 14.6959 psi ≈ 760 mmHg ≈ 29.92 inHg
• 1 psi ≈ 0.0689476 bar ≈ 6.895 kPa
• 1 kPa ≈ 7.5006 mmHg