Free online pressure converter
Pressure is force per unit area. This converter handles all major pressure units — SI, imperial, and meteorological — using exact conversion factors.
How to use
- Enter a pressure value.
- Select the unit you are converting from.
- Select the unit you want to convert to.
- The result and a full conversion table appear instantly.
Supported units
| Unit | Symbol | Notes |
|---|---|---|
| Pascal | Pa | SI base unit |
| Kilopascal | kPa | 1,000 Pa |
| Megapascal | MPa | 1,000,000 Pa |
| Bar | bar | 100,000 Pa exactly |
| Millibar | mbar | 100 Pa; used in meteorology |
| Pound per square inch | psi | US engineering |
| Kilopound per square inch | ksi | Structural engineering |
| Atmosphere | atm | 101,325 Pa exactly |
| Torr | Torr | 1/760 atm |
| Millimeter of mercury | mmHg | Blood pressure, lab |
| Inch of mercury | inHg | Aviation, weather |
| Inch of water | inH₂O | HVAC, medical |
Conversion factors
All units convert through Pascal as the base unit:
| Unit | Pascals |
|---|---|
| 1 atm | 101,325 |
| 1 psi | 6,894.757 |
| 1 bar | 100,000 |
| 1 mmHg | 133.322 |
| 1 inHg | 3,386.39 |
| 1 inH₂O | 249.089 |
Worked example
Convert 2 atm to psi:
2 × 101,325 Pa ÷ 6,894.757 Pa/psi ≈ 29.39 psi
Frequently asked
How is pressure calculated?
Pressure equals force divided by area (P = F/A). One Pascal is one Newton per square meter. Other units scale from this base using fixed conversion ratios.
What is one atmosphere in other units?
One standard atmosphere (atm) equals 101,325 Pa, 14.696 psi, 1.01325 bar, 760 mmHg, and 29.921 inHg. These are exact definitions used in chemistry and physics.
What is the difference between psi and kPa?
Both measure pressure but use different unit systems. 1 psi equals 6.895 kPa. Tires in the US are rated in psi; European tire pressure is often given in bar or kPa.
What is Torr?
The Torr is defined as exactly 1/760 of a standard atmosphere, making it effectively equal to 1 mmHg for most practical purposes. It is named after Evangelista Torricelli.
When would I use inH₂O?
Inches of water column (inH₂O) is common in HVAC, ductwork pressure measurements, and medical equipment like ventilators and spirometers, where pressures are very small.