My car manual says to inflate tires to 35 psi. What is that in atmospheres?

35 ÷ 14.6959 = 2.38 atm. Tire pressure in atmospheres isn't used in the US, but if you're using a gauge calibrated in bar or atm (common in Europe), 35 psi ≈ 2.4 atm ≈ 2.41 bar.

I'm solving a chemistry problem that uses the ideal gas law. My pressure gauge reads 29.4 psi. What value do I use for P?

29.4 psi ÷ 14.6959 = 2.0 atm. The ideal gas law (PV = nRT) works cleanly when P is in atm, V in liters, and T in Kelvin — the gas constant R = 0.08206 L·atm/(mol·K).

A pressure vessel specification shows a working pressure of 150 psi. Is that high compared to atmospheric pressure?

150 psi ÷ 14.696 = 10.2 atm — about 10 times atmospheric pressure. Pressure vessel ratings are typically listed as gauge pressure (above atmospheric), so the absolute pressure inside would be 11.2 atm. Anything above 15 psi gauge is considered a pressure vessel under ASME standards.

What's the difference between gauge pressure (psig) and absolute pressure (psia)?

Gauge pressure is measured relative to atmospheric pressure; absolute pressure adds atmospheric pressure on top. A tire gauge showing 32 psi (psig) means 32 psi above atmosphere, so the absolute pressure is 32 + 14.696 = 46.7 psia = 3.18 atm absolute. Gas law calculations always use absolute pressure.

PSI to Atmospheres (atm) Converter

Enter a value to instantly convert between pressure units.

From

Precision4 dp

1 Pound per Sq. Inch = 0.068 Atmosphere

Key Formulas

Pound per Sq. Inch → Bar

bar = psi × 0.0689476

Bar → Pound per Sq. Inch

psi = bar × 14.5038

Atmosphere → Pound per Sq. Inch

psi = atm × 14.6959

Pound per Sq. Inch → Atmosphere

atm = psi × 0.068046

Formula

atm = psi ÷ 14.6959

PSI (pounds per square inch) is the everyday pressure unit in the United States, used for tire inflation, HVAC systems, and pneumatic tools. The atmosphere (atm) is a scientific unit equal to mean air pressure at sea level — roughly 14.7 psi. Scientists and engineers use atm when comparing pressures to ambient conditions, calculating gas behavior, or working with international standards that don't use PSI.

Source: NIST SP 811, Table B.8

Frequently Asked Questions

Real-World Examples

Standard atmospheric pressure at sea level is defined as 14.696 psi, which equals exactly 1 atm — a useful reference point for calibrating pressure gauges.

14.696 psi = 1 atm

A typical car tire is inflated to 32 psi; a chemistry student calculating gas behavior inside the tire needs the pressure in atmospheres for the ideal gas law.

32 psi = 2.18 atm

A scuba tank is filled to 3,000 psi; a dive instructor teaching gas physics wants students to grasp that this is roughly 204 times the pressure we breathe at the surface.

3000 psi = 204.14 atm

An air compressor for a pneumatic nail gun operates at 100 psi; an engineer sizing the system for a metric-standard specification needed the equivalent in atmospheres.

100 psi = 6.8 atm

psi to bar bar to psi atm to psi kpa to psi psi to kpa

PSI to Atmospheres (atm) Converter

Key Formulas

Formula

Frequently Asked Questions

Real-World Examples

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