psi US customary / imperial
Measures: Pressure — how concentrated a push
Pound per square inch
The US pressure unit — pounds of force on each square inch.
PressureHow it's defined
One pound-force (0.45359237 kg × standard gravity 9.80665 m/s², both exact) spread over one square inch (25.4 mm side, exact) — so 1 psi = 6,894.757293168… Pa, exactly, with a long tail.
1 psi ≈ 6,894.757 Pa — exact (long decimal)car tires run ≈ 30–35 psi
Convert — honestly
psi equals
6894.75729 Pa
Pascal · factor exact — the base unit itself
0.0689475729 bar
Bar · factor exact — exact by definition
Conversions run through the pascal using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.
Where you meet it
- US tire gauges and bike pumps
- Plumbing and compressor specs
Source
This page is an authored summary of the authoritative definition — checkable one click away.
NIST Special Publication 811 — Guide for the Use of the SI