Pressure Calculator
Pressure is force spread over an area. The same force concentrated into a smaller area produces far greater pressure, which is why sharp things cut.
Formula
P = F ÷ A
- P in pascals, F in newtons, A in square metres
- 1 Pa = 1 N/m²; 1 bar = 100,000 Pa
700 N on 0.02 m²: 700 ÷ 0.02 = 35,000 Pa, or 0.35 bar
The Formula
Pressure = Force ÷ Area
Measured in pascals, where one pascal is one newton per square metre.
700 N spread over 0.02 m² gives 35,000 Pa, or 35 kPa.
A pascal is a small unit, so real-world pressures are usually quoted in kilopascals, bar or psi.
Converting Between Units
- 1 bar = 100,000 Pa = 14.5 psi
- 1 atmosphere = 101,325 Pa = 14.7 psi
- 1 psi = 6,895 Pa
Car tyres are typically 2.2–2.5 bar, or 32–36 psi. Note that tyre gauges read gauge pressure, meaning pressure above atmospheric — a "flat" tyre still contains air at roughly 1 bar absolute.
Why Area Matters So Much
Because pressure is force divided by area, shrinking the area multiplies the pressure without changing the force at all.
A drawing pin pushed with modest finger force concentrates it onto a tip of perhaps 0.01 mm², producing enormous local pressure. The same principle explains why snowshoes stop you sinking, why stiletto heels damage floors that an elephant would not, and why a sharp knife cuts with less effort than a blunt one.
Quick Reference
| Unit | In pascals | In bar | In PSI |
|---|---|---|---|
| 1 Pa | 1 | 0.00001 | 0.000145 |
| 1 kPa | 1,000 | 0.01 | 0.145 |
| 1 bar | 100,000 | 1 | 14.504 |
| 1 atm | 101,325 | 1.013 | 14.696 |
| 1 PSI | 6,894.76 | 0.0689 | 1 |
Frequently Asked Questions
- How do I calculate pressure?
- Divide force by the area it acts over. 700 N across 0.02 m² gives 35,000 pascals, or 35 kPa.
- How many psi is 1 bar?
- 14.5 psi. One atmosphere is slightly more at 14.7 psi, which is why the two are often treated as interchangeable in everyday use.
- Why do sharp objects cut more easily?
- A smaller contact area produces far higher pressure for the same force. A sharp edge concentrates your effort into a tiny area.
- What is gauge pressure?
- Pressure measured relative to atmospheric. A tyre gauge reading 32 psi means 32 psi above the surrounding air, not 32 psi absolute.