Convert Atmospheres to PSI

About converting Atmospheres to PSI

Atmospheres (atm) and PSI (psi) are both units of pressure, so converting between them is a single multiplication: multiply your Atmospheres figure by 14.6959. Ten Atmospheres comes to 146.9595 PSI, and a hundred works out at 1,469.59 PSI.

Rule of thumb: going from Atmospheres to PSI multiplies, so the figure always grows — one Atmosphere is already 14.6959 PSI. If your answer came out smaller, you have the conversion the wrong way round.

What is an Atmosphere?

The standard atmosphere is a defined reference rather than a working unit: a figure fixed by agreement at roughly what the air presses at sea level on an ordinary day. Nobody sets a gauge to it. Instead it is the yardstick other pressures are described against — divers count depth in atmospheres, chemists specify reactions at one atmosphere, and test standards quote pressures as multiples of it. Because it is a defined number rather than a measured one, the real pressure outside almost never equals exactly one atmosphere; it wanders with the weather, which is what a barometer is telling you.

What is a PSI?

Pounds per square inch is the pressure unit Americans actually meet: on the gauge at the filling-station air pump, on compressors, on hydraulic equipment, and on the sidewall of every tyre sold in the country. It survives in British tyre pressures too, despite nearly everything else there having gone metric. Structurally it is exactly what the name says — a pound-force resting on a square inch — and that heritage is also its weakness, because it inherits the pound-force and with it the old confusion between pounds as weight and pounds as mass.

To put both in perspective: the pressure 10 metres underwater is about 2 atmospheres, while a car tyre is usually inflated to about 32 psi.

The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the PSI to Atmospheres converter, or browse all Pressure converters.