Convert standard atmospheres to pounds per square inch

One standard atmosphere is 14.6959488 pounds per square inch. To convert any amount, multiply by 14.6959488. Going the other way, one pound per square inch is 0.0680459639 standard atmospheres.

Multiply the standard atmosphere figure by 14.6959488. So psi = atm × 14.6959488. For a quick mental estimate, multiplying by about 14.7 gets you within a percent or so, which is close enough for most everyday purposes.

One standard atmosphere is sea-level air pressure by definition. One standard atmosphere is defined as exactly 101,325 pascals. It is a reference value rather than a measurement of the actual air pressure today.

One pound per square inch is a car tyre runs about 32 psi. Psi is the tyre-pressure unit in North America. Car tyres typically run 30–35 psi, and getting this wrong measurably affects both fuel economy and braking distance.

Yes. Since the 1959 international yard and pound agreement, the imperial and metric systems are related by exact definitions rather than measurements — the inch is exactly 25.4 mm and the pound exactly 0.45359237 kg. Everything derived from those, including this conversion, is therefore exact. Round at the end rather than partway through, since rounding atm before converting introduces an error the conversion then multiplies.