Standard atmospheres to pounds per square inch (atm to psi)

The formula

psi = atm × 14.69594878

Where the factor comes from — each unit by its definition, then its size in SI:

• 1 atm = (standard atmosphere in Pa, CODATA 2022) × Pa = 101,325 Pa
• 1 psi = lbf / in² = 6,894.75729317 Pa

Dividing the two SI sizes gives the factor: 14.6959487755 (rounded for display; the underlying ratio is fixed by the definitions). The reverse factor is 0.0680459639099.

Pressure is force per area; the pascal is one newton per square metre. Tyres are quoted in psi or bar, weather in hPa, blood pressure in mmHg and gas laws in pascals or atmospheres.

Worked examples

• A car tyre (US gauge): 2.17747 atm = 32 psi — 2.17747 × 14.69594878 = 32
• Sea-level air: 1 atm = 14.6959 psi — 1 × 14.69594878 = 14.6959
• A car tyre (European gauge) (2.2 bar): 2.17123 atm = 31.9083 psi — 2.17123 × 14.69594878 = 31.9083
• A systolic blood-pressure reading (120 mmHg): 0.157895 atm = 2.32041 psi — 0.157895 × 14.69594878 = 2.32041

Frequently asked questions