Pressure Converter

Convert between pascals, bar, psi, and atmospheres, with what pressure actually measures explained clearly.

What a Pressure Reading Actually Represents

Pressure is force distributed over an area, which is why every pressure unit is really built from a force unit divided by an area unit, even when the name doesn’t make that obvious. The pascal, the SI unit, is defined as one newton of force per square metre, an extremely small amount of pressure in practical terms, which is why real-world pressures are usually quoted in kilopascals or the much larger bar, itself defined as exactly one hundred thousand pascals and chosen because it sits conveniently close to typical atmospheric pressure at sea level. Atmospheric pressure itself became a natural reference point for a unit, giving us the atmosphere, defined as the average pressure the air exerts at sea level, close to but not identical to one bar. Psi, pounds per square inch, is the standard imperial pressure unit and follows directly from its name — literally the force in pounds divided by the area in square inches it’s spread across — which is why tyre pressure, commonly quoted in psi in the US and bar or kilopascals elsewhere, converts between the two systems using the same underlying force and area conversions already covered by the weight and length units these pressure units are built from.