Free Pressure Converter
Convert pressure units instantly — bar, PSI, Pascal, atmosphere, Torr, kPa, MPa. Type into any field and all others update. Free, symmetrical, no sign-up.
Exact Conversion Formula & Multipliers
Standard atmospheric pressure is fixed at 1 atm = 101,325 pascals exactly, while 1 bar = 100,000 pascals exactly (chosen as a round metric number close to 1 atm for convenience). From these, 1 psi = 6,894.757293168361 Pa and 1 mmHg = 133.322387415 Pa (the conventional value, based on mercury's density at 0°C under standard gravity). This converter keeps atm, bar, and their derived units separate rather than treating them as interchangeable round numbers; it also keeps the torr (exactly 101,325/760 Pa) distinct from the conventional mmHg, although they differ by less than one part in a million.
Practical Real-World Scenarios
- Automotive and cycling: tire pressure is specified in psi in the US and UK but in bar or kPa in most of Europe and Asia, a frequent point of confusion when using a foreign pump gauge.
- Meteorology: barometric pressure is reported in millibars (hectopascals) internationally but in inches of mercury on US weather broadcasts.
- Medicine and diving: blood pressure is measured in mmHg worldwide, while scuba diving depth-pressure calculations typically use bar or atm.
Historical & Technical Background
The 'standard atmosphere' was originally defined by Evangelista Torricelli's 17th-century mercury barometer experiments, which measured air pressure by the height of a mercury column it could support at sea level. The bar (proposed for meteorology in the early 20th century by Vilhelm Bjerknes; William Napier Shaw introduced the millibar into weather reporting) was deliberately chosen close to but distinct from the atmosphere for cleaner metric arithmetic in weather reporting, which is why 1 bar and 1 atm differ by only about 1.3%.
Precision & Accuracy Statement
Conversion factors use the exact defined values given in NIST Special Publication 811 and the BIPM SI Brochure wherever such a definition exists (for example 1 lb = 0.45359237 kg, 1 in = 2.54 cm, 1 US gal = 3.785411784 L, g₀ = 9.80665 m/s²); derived factors are computed from those definitions rather than copied as rounded figures. Results are calculated in double-precision floating point and shown to 10 significant digits, so the last digit can differ by one unit of rounding. The rounded figures in the text and tables above are for reading convenience.
How This Converter Works
Pressure is measured in different units across industries — PSI in the US, bar in Europe, Pascal in science, atmosphere in meteorology. Our converter handles all 8 units simultaneously with symmetrical updating.
Common Conversions
| Pascal (Pa) | Bar | PSI | Atmosphere (atm) |
|---|---|---|---|
| 1 Pa | 0.00001 bar | 0.000145 PSI | 0.00000987 atm |
| 100,000 Pa | 1.0 bar | 14.504 PSI | 0.9869 atm |
| 101,325 Pa | 1.01325 bar | 14.696 PSI | 1.0 atm |
| 6,894.76 Pa | 0.06895 bar | 1.0 PSI | 0.06805 atm |
| 220,632 Pa | 2.2063 bar | 32 PSI | 2.177 atm |