Pressure Converter

Convert pressure between Pa, kPa, bar, psi, atm, mmHg and more

What is it and how does it work?

Pressure is measured in dozens of different units across different industries, regions, and eras — and converting between them correctly is critical in engineering, medicine, meteorology, and everyday DIY tasks. Pascal (Pa) is the SI unit of pressure, but you'll encounter bar, atm (atmospheres), psi (pounds per square inch), mmHg, torr, and inHg (inches of mercury) depending on context. A car tyre rated at 32 psi is also 2.21 bar, 220.6 kPa, or 1656 mmHg.

Understanding which unit is appropriate for which context prevents errors: medical blood pressure uses mmHg; HVAC and gas systems use bar or psi; weather reports use hPa (hectopascals, equivalent to millibar); vacuum systems use torr or Pa; altitude pressure uses atm or kPa. This tool converts between all major pressure units instantly and shows the full conversion table for reference.

Common use cases

• Tyre pressure: convert manufacturer tyre pressure specifications from bar to psi (or vice versa) depending on whether your tyre gauge uses imperial or metric units.
• Blood pressure: understand a medical reading of 120/80 mmHg in kPa (16.0 / 10.7 kPa) for international medical literature or non-mmHg patient monitors.
• Weather reports: convert hPa from a European weather forecast to inHg for a US barometer reading, or to atm for science reference.

Frequently asked questions

What is the difference between Pa, hPa, kPa, and MPa?

These are SI multiples of Pascal. 1 hPa = 100 Pa = 1 mbar (commonly used in meteorology). 1 kPa = 1000 Pa (used for medical and industrial pressures). 1 MPa = 1,000,000 Pa (used for hydraulic systems). Standard atmospheric pressure is 101.325 kPa = 1013.25 hPa.

What is the difference between psi and bar?

1 bar ≈ 14.504 psi. Bar is the metric unit most commonly used in European tyre, gas, and fluid system specifications. PSI (pounds per square inch) is the imperial equivalent, dominant in North American automotive and plumbing contexts.

What is the difference between torr and mmHg?

They are very nearly identical — 1 torr = 1/760 of a standard atmosphere; 1 mmHg = the pressure exerted by 1 mm of mercury at 0°C. The difference is less than 0.000015%. In practice they are used interchangeably for vacuum and medical measurements.

What is gauge pressure vs. absolute pressure?

Absolute pressure is measured relative to a perfect vacuum (0 pressure). Gauge pressure is measured relative to atmospheric pressure — so a gauge reading of 0 psi means atmospheric pressure, not vacuum. Tyre pressures are gauge pressures; weather pressures are absolute pressures. When converting, be clear which reference is being used.

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