Pressure Calculator (P = F/A)

Pressure Calculator works with the definition of pressure: a force spread over an area, P = F ÷ A. Enter any two of pressure, force and area and the third is worked out, with the formula and the working in SI units. Units can be mixed freely — pressure in pascals, kilopascals, megapascals, hectopascals (the same as millibars), bar, standard atmospheres, pounds per square inch, millimetres of mercury or torr; force in newtons, kilonewtons, kilogram-force or pound-force; area in square metres, centimetres, millimetres, kilometres, inches or feet. Under the answer, the pressure is listed in every one of those units, so the page doubles as a pressure unit converter: tyre pressure in psi and bar, weather pressure in hPa or mmHg, or the pressure a shoe heel puts on a floor.

1. Type two of the three values and choose units for each.
2. Leave the third empty: it is worked out and highlighted.
3. Read the same pressure in every other unit in the table below the answer.
4. Change a unit to recalculate in it. Clear all starts again.

• It assumes the force is spread evenly and acts at right angles to the surface. A point load, or a force at an angle, gives a higher local pressure.
• Pressures here are as calculated, not gauge or absolute: a tyre gauge reads pressure above the surrounding air, so add about 1 atm for the absolute value.
• Fluid pressure at a depth (ρ × g × h) is not built in; work it out as a force over an area, or use the potential energy page for the height side.
• Torr and mmHg differ by about 0.14 parts per million: torr is exactly 1/760 of an atmosphere, mmHg is defined from mercury’s density. For blood pressure the difference does not matter.
• The calculation happens in your browser. Nothing you enter leaves it.

Enter the pressure in psi with any force and area, or simply read the table: 1 psi is 0.0689476 bar, so a 32 psi tyre is 2.21 bar.

The same body weight on a tiny area makes a huge pressure. 700 N on 1 cm² is 7,000 kPa; spread over 300 cm² of flat soles it is about 23 kPa.

Standard atmospheric pressure is 101,325 Pa exactly — 1,013.25 hPa, 1.01325 bar, 760 torr or about 14.696 psi. Weather pressure at sea level varies around it.

Yes, by definition. The pascal is small: a sheet of paper resting on a table presses about 1 Pa, which is why kilopascals and bar are more common in practice.