Pressure Calculator
Calculate pressure from force over area, or the pressure at depth in a fluid.
Please note: Results use idealised models — point masses, no air resistance, ideal gases and uniform materials. Real experiments deviate. Use these for study and estimation, not for engineering sign-off.
What the Pressure Calculator does
Pressure is force divided by the area it acts on. Spread a force over a large area and the pressure is gentle; concentrate it into a point and the same force becomes enormous. In a fluid, pressure instead builds with the weight of everything above, so it depends only on depth and density.
Formula
P = F ÷ AP = ρ × g × h (hydrostatic, gauge)P_absolute = P_gauge + P_surface1 atm = 101,325 Pa = 14.696 psi
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Calculate pressure from | one of 2 options | Yes | — |
| Force | number | In some modes | Shown Calculate pressure from is Force spread over an area. |
| Force unit | one of 5 options | In some modes | Shown Calculate pressure from is Force spread over an area. |
| Area | number | In some modes | Shown Calculate pressure from is Force spread over an area. |
| Area unit | one of 5 options | In some modes | Shown Calculate pressure from is Force spread over an area. |
| Fluid | one of 13 options | In some modes | Shown Calculate pressure from is Depth in a fluid. |
| Depth | number | In some modes | Shown Calculate pressure from is Depth in a fluid. |
| Depth unit | one of 9 options | In some modes | Shown Calculate pressure from is Depth in a fluid. |
| Surface pressure | Pa | Optional | Standard atmosphere is 101,325 Pa. Set to 0 for gauge pressure only. Accepts 0 or more. Shown Calculate pressure from is Depth in a fluid. |
| Gravitational acceleration | m/s² | Optional | Standard gravity on Earth is 9.80665 m/s². The Moon is 1.62, Mars 3.72. Accepts 0 or more. Shown Calculate pressure from is Depth in a fluid. |
How to use it
- Choose Calculate pressure from.
- Fill in the remaining inputs the form shows for your choice.
- Select Calculate.
Worked example
A diver 10 m down in fresh water.
- Fluid
- Water (1000 kg/m³)
- Depth
- 10 m
- Surface pressure
- 101,325 Pa
Gauge = 1000 × 9.80665 × 10 = 98,067 Pa. Absolute = 199,392 Pa, which is 1.968 atm — nearly double the pressure at the surface.
Frequently asked questions
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to the surrounding atmosphere and is what most instruments show. Absolute pressure includes the atmosphere, and is what the gas laws require.
Does the shape of a container change the pressure at the bottom?
No. Pressure at a given depth depends only on depth, fluid density and gravity — a result known as the hydrostatic paradox.