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Pressure Converter

Convert between pascal, kilopascal, megapascal, bar, millibar, PSI, atmosphere, mmHg, torr, inHg, kgf/cm², and more — all pressure units at once.

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All conversions from 1 pascal

Unit	Symbol	Value

About This Tool

How this pressure converter reconciles twenty four units built from two entirely different measuring traditions

Pressure units split roughly into two families. One family measures force spread over a defined area, which is where PSI and kgf per square centimetre come from. The other measures how high a column of liquid rises under that pressure, which is where millimetres of mercury and inches of water come from. Both are legitimate ways to describe the same physical quantity, and this tool converts freely between them by routing everything through the pascal.

All arithmetic happens client side in JavaScript. Nothing is uploaded, logged, or sent to a server.

Why the pascal is the hub

The pascal is the SI derived unit of pressure, defined by the BIPM as one newton of force per square metre of area. It is small in everyday terms, atmospheric pressure at sea level is over one hundred thousand pascals, which is exactly why kilopascals, bar, and PSI exist as more convenient everyday scales.

Step 1 Convert input to pascals The entered value is multiplied by its unit's pascal equivalent. Entering 2 bar becomes 2 times 100,000, or 200,000 pascals.

Step 2 Divide into the target unit That pascal figure divides by the target's factor. Converting 200,000 pascals to PSI divides by 6894.757.

Step 3 Fill the comparison table The same pascal figure is divided against all twenty four units at once, so you see the value expressed in bar, atmospheres, mercury columns and force per area units side by side.

// adapted from the tool source, factor is pascals per 1 unit var PR = [ { key: 'bar', factor: 1e5 }, { key: 'psi', factor: 6894.757 }, { key: 'atm', factor: 101325 }, { key: 'mmhg', factor: 133.322387 } ]; var pa = val * fromUnit.factor; var result = pa / toUnit.factor;

Unit	Symbol	Pascals per unit
Pascal	Pa	1
Hectopascal	hPa	100
Kilopascal	kPa	1,000
Megapascal	MPa	1,000,000
Gigapascal	GPa	1,000,000,000
Bar	bar	100,000
Millibar	mbar	100
Microbar	µbar	0.1
PSI (pound per sq in)	psi	6,894.757
Kilopound per sq in	ksi	6,894,757
Standard atmosphere	atm	101,325
Technical atmosphere	at	98,066.5
mmHg (mercury)	mmHg	133.322387
Torr	Torr	133.322368
Inch of mercury	inHg	3,386.389
Inch of water	inH₂O	249.0889
Millimetre of water	mmH₂O	9.80665
kgf per sq cm	kgf/cm²	98,066.5
Dyne per sq cm	dyn/cm²	0.1
Pound per sq ft	psf	47.880259
Centimetre of mercury	cmHg	1,333.22387
Millitorr	mTorr	0.133322368
Centimetre of water	cmH₂O	98.0665
Foot of water	ftH₂O	2,989.06692

Torr and mmHg are close but not identical. The torr was defined later as exactly 1/760 of a standard atmosphere, which works out to 133.322368 pascals, while the older millimetre of mercury figure, based on an actual mercury column under standard gravity, comes to 133.322387 pascals. The tool keeps both entries with their own slightly different factors rather than treating them as one unit, matching the small but real historical divergence between the two definitions.

Two atmospheres, not one

Standard atmosphere

Fixed by international agreement at exactly 101,325 pascals, representing typical air pressure at sea level. Used as the reference for defining the torr and for aviation and meteorology baselines.

Technical atmosphere

An older engineering convention equal to exactly one kilogram force per square centimetre, working out to 98,066.5 pascals. It predates the SI system and still appears in some European industrial equipment specs.

SI derived unit, pascal = newton/m² PSI in US engineering and tire pressure mmHg in medicine and meteorology

Pressure standard references

BIPM SI Brochure defines the pascal as the SI coherent derived unit of pressure, one newton per square metre.
NIST guide to SI pressure units covers the standard atmosphere and its exact fixed value.
ISO 80000-4 is the international standard defining mechanical quantities including pressure and its accepted non-SI units.

Pressure readings in context

Checking tire pressure specs given in PSI against a bar reading on a European pump, converting a weather report's hectopascal figure into inches of mercury for an American barometer, reading a blood pressure cuff's mmHg output alongside a kilopascal figure from a medical device, and translating an industrial gauge reading between bar and technical atmosphere on imported machinery.

Common Questions

Frequently asked questions

How many psi is 1 bar?

1 bar is about 14.5038 psi, and 1 psi is about 0.0689 bar. A car tyre at 2.2 bar is about 32 psi.

What is standard atmospheric pressure?

One standard atmosphere is exactly 101,325 Pa. That is 1.01325 bar, 1,013.25 hPa, 760 Torr and about 14.696 psi.

Are mmHg and Torr the same?

Almost. One Torr is exactly 1/760 of a standard atmosphere, 133.322368 Pa. One conventional mmHg is 133.322387 Pa. The gap is about one part in seven million, so for blood pressure or weather they are interchangeable.

Why do weather reports use hPa or millibars?

A hectopascal and a millibar are the same size, 100 Pa. Meteorologists kept the millibar scale when they moved to SI units, so 1013 mbar and 1013 hPa describe the same air pressure.

Is this pressure converter free?

Yes. It is free, needs no sign up, and all conversions run in your browser. Nothing you enter is sent to a server.

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