Pressure Unit Converter
Type a pressure into any field below and the other five update instantly. Covers the six units used across every gas law calculator on this site.
Pressure Converter
Common Pressure Conversion Factors
| 1 Unit | Equals |
|---|---|
| 1 atm | 101,325 Pa |
| 1 atm | 101.325 kPa |
| 1 atm | 1.01325 bar |
| 1 atm | 760 mmHg |
| 1 atm | 760 torr |
| 1 atm | 14.6959 psi |
| 1 bar | 100,000 Pa |
| 1 psi | 6,894.76 Pa |
Pressure units multiplied on chemistry, physics, and engineering fields for historical reasons. Barometers used mercury columns (mmHg, torr), meteorology and general chemistry standardized on the atmosphere (atm), the SI system defined the pascal (Pa) from first principles, and US customary engineering kept pounds-per-square-inch (psi).
All of them describe the same physical quantity, force per unit area, just scaled differently, which is why converting between them is always a simple multiplication, never an offset like temperature conversion requires.
Whichever unit your textbook, lab manual, or datasheet uses, every gas law calculator on this site, Boyle's Law, the ideal gas law, and the combined gas law solver, accepts it directly.
Worked Example: Converting a Tire Pressure Reading
Problem: A tire pressure gauge reads 32 psi. What is this in kPa, and how many atmospheres is it?
Note that a car tire's 32 psi reading is a gauge pressure, measured relative to atmospheric pressure, not relative to a total vacuum. The absolute pressure inside the tire is actually about 32 + 14.7 = 46.7 psi, since atmospheric pressure is already pushing on the tire from outside. This gauge-versus-absolute distinction matters whenever a real-world pressure reading feeds into a gas law calculation, since Boyle's Law, the ideal gas law, and every other calculator on this site expect absolute pressure, not gauge pressure.
Common Mistakes When Converting Pressure Units
The most common mistake is confusing gauge pressure with absolute pressure, as shown in the worked example above. Most everyday pressure gauges, tire gauges, blood pressure cuffs, most industrial pressure gauges, read relative to atmospheric pressure, so a reading of 0 psi gauge is actually about 14.7 psi absolute. Gas law calculators always need absolute pressure, so failing to add atmospheric pressure back in when converting a gauge reading is a frequent and easy-to-miss source of error.
A second mistake is treating mmHg and torr as if they were exactly identical in every context, they differ by less than 0.001%, which is negligible for virtually all practical purposes, but precision scientific work occasionally does distinguish them, so it's worth knowing they aren't perfectly interchangeable even though they're treated that way almost everywhere else.
A third pitfall is rounding conversion factors too aggressively during multi-step conversions. Converting psi to atm to kPa in two separate rounded steps can introduce more error than converting directly with a single precise factor. When precision matters, convert directly between your starting and ending unit rather than chaining several rounded intermediate conversions.
Finally, always double-check which unit a data source is actually reporting. Engineering specifications from different countries and industries mix Pa, bar, psi, and atm freely, and assuming the wrong one (especially confusing bar with atm, which are close but not identical) is one of the most common real-world sources of pressure-related calculation errors.