Pressure Converter

What is pressure?

Pressure is force distributed over an area. Squeezing a balloon, the weight of the atmosphere on your shoulders, and the air in a car tire are all pressure. Formally, pressure = force ÷ area. The pascal (Pa) is the SI unit: one newton of force spread over one square meter (1 Pa = 1 N/m²). A pascal is small, so everyday pressure is usually expressed in kilopascals, bars, or PSI. A versatile pressure converter saves you from memorizing a long table of factors.

Why so many pressure units?

Meteorologists use hectopascals/kilopascals; European car tires use bar; American tires use PSI; scuba divers read atm or bar; laboratories and medicine use Torr or mmHg for vacuum and blood pressure. Each unit fits the scale and tradition of its field. Our tool connects all of them through the pascal.

The base-unit method

Every value is first converted into pascals (the base unit), then from pascals into your target unit. This keeps the arithmetic to simple ratios and yields results accurate to six decimals. For example, to convert bar to PSI: 1 bar = 100,000 Pa, and 1 PSI = 6894.757 Pa, so 1 bar = 100,000 ÷ 6894.757 = 14.5038 PSI.

Key conversion factors

• 1 pascal = 1 Pa (the definition)
• 1 kilopascal = 1000 Pa
• 1 bar = 100,000 Pa
• 1 PSI = 6894.757293 Pa
• 1 atmosphere = 101,325 Pa
• 1 Torr = 133.322368 Pa (760 Torr = 1 atm)
• 1 mmHg = 133.322387 Pa

Torr vs mmHg — close but not identical

Two units that trip people up are Torr and mmHg (millimeter of mercury). By definition, 1 standard atmosphere = exactly 760 Torr = 101,325 Pa, so 1 Torr = 133.322368 Pa. A millimeter of mercury, the height a column of mercury rises under gravity, equals 133.322387 Pa. The difference is about 0.000015%, negligible for almost all practical work but worth knowing in metrology and vacuum science. Our tool keeps both so you can match the convention your field expects.

Standard atmosphere

Sea-level atmospheric pressure is defined as exactly 1 atm = 101,325 Pa. That single value threads through everything: 1 atm = 1.01325 bar = 14.6959 PSI = 760 Torr = 760 mmHg. When you see a weather report of "1013 hPa," that is 1013 hectopascals = 101.3 kPa ≈ 1 atm — typical fair-weather pressure at sea level.

Real-world examples

A properly inflated car tire is about 32 PSI ≈ 2.21 bar ≈ 221 kPa. A scuba tank is filled to roughly 200 bar ≈ 2900 PSI. Blood pressure of "120/80 mmHg" is 120 over 80 millimeters of mercury — about 16 kPa over 10.7 kPa. Weather systems differ from "high 1030 hPa" to "storm 980 hPa." A vacuum pump might reach 1 Torr, a thousand times thinner than atmosphere. The converter handles all these spans in one step.

Common mistakes

The main error is assuming bar and atm are interchangeable — they differ by 1.3% (1 atm = 1.01325 bar), which is fine for casual talk but not for engineering. Another is mixing gauge and absolute pressure: a tire gauge reads PSI above atmosphere, while "psia" is absolute. Our converter treats the numeric value as given; add 14.7 PSI to a gauge reading if you need absolute. Finally, don't round PSI too early — 1 bar is 14.5038, not 14.5, and small rounding compounds in calculations.

Frequently asked questions