Pounds per Square Inch to Atmospheres

Pounds per square inch and atmospheres

One psi is the pressure of one pound-force on one square inch: about 6,894.757 pascals, derived from exact definitions. Tire pressure in the US and UK, air compressors, pressure washers and plumbing use psi.

The standard atmosphere is defined as exactly 101,325 pascals, the average air pressure at sea level. Chemistry, diving depth (1 atm per 10 m of water) and gas laws use atmospheres.

Worked example

Convert 100 psi: 100 × 0.06804596391 = 6.804596391, so 100 pounds per square inch is 6.804596391 atmospheres. Likewise 200 psi = 13.60919278 atm.

Estimating in your head

Divide by 15 for a quick figure; it is off by about 2.1%. For 100 psi that gives 6.67 atm, against 6.8046 exactly.

Going the other way

To convert atmospheres to pounds per square inch, divide by 0.06804596391 (or multiply by 14.6959487755). The swap button between the boxes opens that page.

atm = psi × 0.06804596391

1 psi = ≈ 6,894.757293 Pa and 1 atm = 101,325 Pa, both by definition, so the factor is their ratio: 0.06804596391 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.