Pressure Calculator

Pressure is defined as the force applied perpendicular to a surface divided by the area over which it acts: P = F/A. It appears everywhere in science and engineering, from atmospheric pressure to tyre inflation, hydraulic systems, fluid mechanics, and structural loading. The SI unit of pressure is the pascal (Pa), equal to one newton per square metre, but in practice you will also encounter kilopascals (kPa), megapascals (MPa), bar, atmospheres (atm), and pounds per square inch (psi). This calculator covers two modes. In the first you enter a force and an area and it returns the pressure in all five common units simultaneously. In the second mode you calculate hydrostatic or fluid pressure at a given depth: P = ρgh, where ρ is the fluid density in kg/m3, g is gravity, and h is depth in metres. This formula gives the pressure due to the weight of fluid above a point, which is the gauge pressure, the pressure above atmospheric. The default example uses a force of 1,000 N on an area of 0.25 m2, giving a pressure of 4,000 Pa (4 kPa, 0.58 psi). This is a common physics problem format: a block of known weight standing on a known base area. The fluid mode uses water (1,000 kg/m3) as its default, which makes it easy to find the pressure at any dive depth. The calculator produces all unit conversions at once, saving you from having to look up conversion factors. Results update as you type. Use this for physics homework, plumbing and hydraulics, weather and atmospheric problems, or any engineering application involving pressure.

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N
m²
4,000 Pa
pressure
In kPa4.000 kPa
In psi0.580 psi
In bar / atm0.0400 bar / 0.0395 atm

P = F/A in pascals. Fluid mode gives gauge pressure only (pressure due to fluid above, not including atmosphere). Rounded for display.

How it works

From force and area: P = F/A in pascals. Conversions: 1 kPa = 1,000 Pa; 1 bar = 100,000 Pa; 1 atm = 101,325 Pa; 1 psi = 6,894.76 Pa. Fluid (hydrostatic gauge) pressure: P = ρgh, where ρ is density in kg/m³, g is gravity, and h is depth in metres. This gives the pressure due to the weight of fluid above the point, not including atmospheric pressure.

Worked example

A 1,000 N force is applied to a surface of area 0.25 m². Pressure = 1,000 / 0.25 = 4,000 Pa. In kPa: 4.000 kPa. In psi: 4,000 / 6,894.76 = 0.580 psi. In bar: 4,000 / 100,000 = 0.040 bar. These match the default values pre-filled above.

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Frequently asked questions

What is the formula for pressure?

Pressure equals force divided by area: P = F/A. In SI units force is in newtons and area in square metres, giving pressure in pascals (Pa). One pascal is one newton per square metre. A 1,000 N force on a 0.25 m2 surface gives a pressure of 4,000 Pa or 4 kPa.

How is fluid pressure calculated?

Fluid or hydrostatic pressure at a depth h equals the fluid density rho times gravity g times depth: P = rho g h. For water (rho = 1000 kg/m3) at 10 m depth: P = 1000 times 9.81 times 10 = 98,100 Pa, or about 98.1 kPa, which is close to 1 atmosphere of gauge pressure.

How do you convert pascals to psi or bar?

To convert from pascals: divide by 6894.76 for psi, divide by 100,000 for bar, or divide by 101,325 for atm. So 4,000 Pa equals approximately 0.58 psi, 0.04 bar, and 0.039 atm. This calculator performs all four conversions simultaneously.