Pressure Calculator
Solve P = F ÷ A for pressure, force or area, with selectable pressure units.
What is Pressure?
Pressure is force spread over an area: P = F ÷ A. The same force over a smaller area gives a larger pressure, which is why a sharp knife cuts and a nail goes into wood — and why snowshoes spread the same weight over a larger area instead.
How it works
P = F ÷ A, rearranged for whichever field is blank. Forces in newtons, kilonewtons or pounds-force and areas in square metres, centimetres, millimetres or feet are converted to the base pair, and the pressure can be displayed in any of seven units — including mmHg and atmospheres, which is what a barometer or a tyre gauge actually reads.
- Enter what you know. Every field recalculates as you type — there is no submit button. Leave the quantity you want blank and the page solves for it.
- Read the answer and the working. The result appears above the fold; underneath it is the formula with your numbers substituted, so the arithmetic can be checked rather than trusted.
- Check the units and the size. Units are shown on every value and selectable per field, so a result in kJ, kPa or km/h is converted rather than assumed. Sanity-check the magnitude against a known landmark such as 1 g/cm³ for water.
Examples
A textbook problem with a known answer
Every tool here is checked against standard example problems — the molar mass of C6H12O6 is 180.16 g/mol, and free fall from 20 m takes about 2.02 s at g = 9.8 m/s².
A result you want to reason backwards from
Leave the quantity you already know blank instead: given the final answer, most tools recover the starting value — the mass needed for a target concentration, or the height a fall must have had.
Common mistakes
Forgetting that a formula is only as good as its subscripts
H2O and H2O2 are different compounds. The formula field shows its parse — element by element — so a mis-typed subscript is visible before it reaches the arithmetic.
Mixing units in the middle of a calculation
The most common source of a wrong answer is a value in grams next to a formula expecting kilograms, or Celsius next to a gas constant expecting kelvin. This category converts on the way in and labels what it used.
Frequently asked questions
Why does a sharp knife cut more easily?
Because the same force is concentrated onto a much smaller edge area, and pressure is force divided by area. Sharpening does not add force — it subtracts area.
What is atmospheric pressure in different units?
1 atm equals 101 325 Pa, 101.3 kPa, 1.013 bar, 760 mmHg or 14.7 psi. All of those are selectable here, and the Pressure converter in Units & Numbers converts between them.
Is pressure a vector?
No. Pressure acts equally in all directions at a point and has no direction, which is why it is a scalar unlike the force that causes it.