Atmospheres to PSI Converter

The atmosphere is a fixed unit, defined in this converter as 101,325 Pa, and 1 atm = 14.6959 psi. You will mostly meet it in chemistry and physics problems that use gas laws, in older pressure-vessel and lab-equipment specs, and in diving, where depth is often described in atmospheres.

• 2 atm = 29.3919 psi
• 4 atm = 58.7838 psi
• 10 atm = 146.96 psi
• 0.5 atm = 7.348 psi

Because the unit is fixed, it does not change with the weather or your altitude. Real air pressure at your location does.

Pressures in atm are usually absolute: measured from a perfect vacuum. A tyre or compressor gauge, on the other hand, reads how far you are above the air around it. To estimate what a gauge would show at sea level, convert to psi and subtract one atmosphere, 14.6959 psi:

The converter does the unit step only. The subtraction is yours, and skipping it is the classic way to be off by almost 15 psi.

Divers describe pressure at depth in atmospheres because the arithmetic is simple: roughly every 10 metres of seawater adds about one more atmosphere on top of the one from the air. At around 20 metres you are near 3 atm absolute, which this page converts to 44.0878 psia. Treat that as a rule of thumb, since water density varies, and use your dive computer or tables for anything that matters.

Multiplying by 14.7 is only 0.028% high, close enough for any practical use: 3 atm × 14.7 = 44.1 psi. Rounding to ×15 is 2.1% high.

People often swap atm and bar as if they were equal. In this converter 1 atm is 1.0132 bar, so treating them as the same introduces an error of about 1.3%. That is small for a tyre, but it adds up in a calculation that multiplies pressures together.