# Hydrostatic Pressure Calculator

> Work out gauge and absolute pressure at a depth in water or any liquid, or the depth that gives a chosen pressure, from density, depth and g.

Category: Science & engineering · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/hydrostatic-pressure-calculator

Pressure in a still liquid rises with depth by ρ g h, regardless of the container’s shape. Add the pressure at the surface to get the absolute pressure.

Also called: Pressure at depth calculator, Water head pressure calculator.

## Inputs
- Solve for (options: Pressure, Depth; default pressure)
- Liquid density (default 1000)
- Density unit (options: kg/m³, g/cm³, lb/ft³; default kgm3)
- Depth below the surface (default 10)
- Depth unit (options: metres (m), centimetres (cm), millimetres (mm), kilometres (km), feet (ft), inches (in), miles (mi); default m)
- Gauge pressure (default 100)
- Pressure unit (options: pascals (Pa), kilopascals (kPa), megapascals (MPa), bar, atmospheres (atm), psi, mmHg; default kpa)
- Pressure at the surface (unit kPa; default 101.325)
- Gravitational acceleration (g) (unit m/s²; default 9.80665)

## Results
- Result
- Gauge pressure
- Absolute pressure
- Gauge pressure
- Gauge pressure
- Absolute pressure
- Depth
- Depth

## Formula

```
P_gauge = ρ g h;  P_abs = P_surface + ρ g h;  h = P_gauge ÷ (ρ g)
```

Where:
- ρ: liquid density in kg/m³
- g: gravitational acceleration
- h: vertical depth below the free surface in m
- P_surface: pressure acting on the surface (atmospheric if open to air)

## Worked example
1. P_gauge = 1,000 × 9.80665 × 10 = 98,066.5 Pa = 98.0665 kPa.
2. P_abs = 101.325 + 98.0665 = 199.39 kPa, about 1.97 atm.

**Result:** Ten metres down in fresh water the pressure is about 98 kPa above atmospheric, so roughly double the surface pressure in absolute terms.

## What the result means

Divers use the rule of thumb that every 10 m of seawater adds about one atmosphere. Tank walls and dams must resist pressure that grows linearly with depth, so the bottom carries the most load.

## Assumptions and limits
- Liquid at rest with constant density (incompressible).
- Density changes with temperature and salinity; very deep ocean water is slightly compressed.
- Not for moving fluids; see the Bernoulli Equation Calculator.

## Questions

### Does the shape of the container matter?

No. Pressure depends only on the vertical depth, not on the volume or shape above (the hydrostatic paradox).

### What is the difference between gauge and absolute pressure?

Gauge pressure is measured relative to the atmosphere; absolute pressure includes it. Tyre gauges read gauge pressure.

## Sources
- [BIPM: The International System of Units (SI)](https://www.bipm.org/)

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- [Pressure Calculator](https://calculators.geekmidst.com/calculators/pressure-calculator)
- [Buoyancy Calculator](https://calculators.geekmidst.com/calculators/buoyancy-calculator)
- [Bernoulli Equation Calculator](https://calculators.geekmidst.com/calculators/bernoulli-equation-calculator)
- [Density Calculator](https://calculators.geekmidst.com/calculators/density-calculator)

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/hydrostatic-pressure-calculator