Pound per Square Inch (psi) is a pressure unit with the symbol psi. Psi expresses pressure as pounds-force applied over one square inch of area. In Xunits pressure conversions, 1 psi equals 6,894.757293168 pascals.
Quick facts
- Unit name
- Pound per Square Inch
- Symbol
- psi
- Quantity
- pressure
- SI bridge
- 1 psi = 6,894.75729317 Pa
- Category
- Pressure
- Converter hub
- Pressure converter
Pressure scale
Pressure units are easiest to compare through pascals. This visual places psi beside neighboring pressure units.
Definition
Psi expresses pressure as pounds-force applied over one square inch of area. In Xunits pressure conversions, 1 psi equals 6,894.757293168 pascals. The pressure reference matters. psig means gauge pressure relative to local atmosphere; psia means absolute pressure relative to vacuum. A calculator can convert the unit, but it cannot infer the missing reference label.
Pressure reference
A pressure number can be gauge, absolute, or differential. The unit psi tells you the scale, but the surrounding notation tells you the reference. Keep labels such as psig, psia, barg, bara, absolute pressure, or differential pressure when the source provides them.
Exact relationships and reference values
| Relationship | Why it matters |
|---|---|
| 1 psi = 6,894.757293168 Pa | Useful reference relationship |
| 1 psi = 6.894757293 kPa | Useful reference relationship |
| 1 bar = 14.5037738 psi | Useful reference relationship |
| 30 psi = about 2.07 bar | Useful reference relationship |
Where psi is used
Psi is common in tire pressure, air compressors, pneumatic tools, hydraulic systems, pressure washers, fuel systems, cylinders, and US industrial equipment labels.
Common mistakes
- Do not treat psi, psig, and psia as interchangeable labels.
- Do not round 1 bar to 15 psi when a gauge setting or specification needs precision.
- Do not compare psi with kPa or bar unless both values use the same pressure reference.
Converters and formulas
Use these pages when you need a direct calculation involving psi.
Related pressure guides
Compare psi with other pressure units in the same directory.
FAQ
What does psi stand for?
Psi stands for pounds per square inch.
What is the difference between psi, psig, and psia?
Psi names the unit. psig is gauge pressure relative to atmosphere. psia is absolute pressure relative to vacuum.
Why is psi common for tire pressure?
US vehicle labels, air pumps, and tire gauges traditionally use psi, so it remains familiar for drivers and mechanics.