Pressure Unit Converter
Pressure is force per unit area, and converting it shows up everywhere from weather and medicine to tyre inflators, diving cylinders and HVAC specs. Enter a value in any one unit and instantly see all 14 common pressure units side-by-side — Pa, hPa, kPa, MPa, bar, mbar, atm, psi, mmHg, Torr, inHg, inH₂O, cmH₂O and kgf/cm².
Please enter a valid number
Live value in every pressure unit
Tip: 1 atm = 760 mmHg ≈ 14.696 psi ≈ 1.01325 bar. Weather "hectopascals (hPa)" share the same number as millibars (mbar).
- atm Sea-level standard atmosphere (= 1 atm)
- psi Car tyres, bike pumps, US industry
- kPa Met-office air pressure, engineering
- bar Diving, automotive, European industry
- mmHg Blood pressure, legacy barometers (≈ Torr)
- inHg US aviation altimeters, weather reports
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Formula
Every unit is converted into pascals (Pa) and then divided by the target unit’s pascal-equivalent.
- · 1 atm = 101 325 Pa exactly — the BIPM definition of standard atmosphere.
- · 1 bar = 100 000 Pa exactly (ISO 80000); 1 mbar = 1 hPa = 100 Pa.
- · 1 psi ≈ 6 894.757 Pa; 1 atm ≈ 14.696 psi (NIST SP 811).
- · 1 mmHg = 133.322 387 Pa (NIST conventional); within one ppm of 1 Torr.
- · 1 inHg ≈ 3 386.39 Pa — common in US aviation altimeters and weather reports.
- · Negative values are accepted for vacuum / gauge readings; absolute zero pressure = 0 Pa is the physical floor.
- · Sources: NIST SP 811 App. B (2008 ed.), BIPM SI Brochure 9th ed., ISO 80000-4.
Frequently asked
My tyre placard says 32 psi — what is that in kPa or bar?
32 psi ≈ 220.6 kPa ≈ 2.21 bar. Most Hong Kong forecourt inflators read in kPa or bar but the door-jamb placard is typically printed in psi — this tool flips between them in one click.
Why are blood-pressure readings in mmHg and not kPa?
Mercury sphygmomanometers literally measured the height of a mercury column, so mmHg became the medical standard and stuck even after digital cuffs took over. 120/80 mmHg ≈ 16.0/10.7 kPa — same pressure, different unit.
Are hPa and mbar the same thing?
Yes — numerically identical: 1 hPa = 1 mbar = 100 Pa. Meteorology shifted from mbar to hPa in the 1980s to align with SI, but the numbers stayed the same. "1013 hPa" and "1013 mbar" describe the same pressure.
What pressure unit do divers use?
Recreational diving uses bar (European gear) or psi (North-American gear). Rule of thumb: every 10 m of seawater adds roughly 1 bar; a 3 000 psi cylinder is ≈ 207 bar. Use this tool to flip between gauges in either standard.
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