Calculator inputs
Formula reference
| Purpose | Formula | Meaning |
|---|---|---|
| Hydrostatic pressure | P = ρgh | Pressure caused by liquid depth. |
| Water head | h = P ÷ (ρg) | Equivalent vertical liquid height. |
| Force on a surface | F = PA | Total perpendicular force over an area. |
| Pressure from force | P = F ÷ A | Average pressure applied to a surface. |
| Elevation pressure change | ΔP = ρgΔh | Static pressure gain or loss. |
| Outlet pressure | Pout = Psource + ρgΔh − Ploss | Estimated pressure after elevation and losses. |
How to use this calculator
- Select the calculation mode matching your problem.
- Choose freshwater, seawater, or a custom liquid.
- Enter vertical heights, pressures, forces, areas, or losses.
- Select gauge or absolute pressure where requested.
- Choose output units and decimal precision.
- Review formulas, steps, warnings, and downloadable results.
Static pressure depends on vertical elevation, not pipe route length. Real systems may also include velocity, friction, pump, valve, and transient effects. Use engineering standards for final equipment and safety decisions.
Example data
| Scenario | Input | Approximate result |
|---|---|---|
| Freshwater depth | 10 m at 20°C | About 97.9 kPa gauge |
| Water head | 100 kPa gauge | About 10.2 m |
| Pressure force | 50 kPa over 2 m² | 100 kN |
| Elevation drop | 30 m downward | About 294 kPa gain |
| Required head | 200 kPa gauge | About 20.4 m |
Water pressure guidance
Gauge and absolute pressure
Gauge pressure uses local atmospheric pressure as zero. Absolute pressure uses a perfect vacuum as zero. The calculator converts between both systems.
Pressure and flow are different
Pressure is energy per unit volume. Flow is volume moving during time. Pipe size and resistance strongly affect flow.
Static and dynamic systems
Hydrostatic calculations assume fluid at rest. Moving water creates friction and velocity effects. Pumps and valves can change pressure significantly.
Frequently asked questions
1. How much pressure does one metre of water create?
One metre of freshwater creates about 9.81 kPa. This value changes slightly with density and gravity.
2. Is water pressure based on tank volume?
No. Static pressure mainly depends on vertical liquid depth. Tank shape and total volume do not directly control bottom pressure.
3. What is gauge pressure?
Gauge pressure is measured relative to atmospheric pressure. A reading of zero gauge means atmospheric pressure.
4. What is absolute pressure?
Absolute pressure is measured relative to a perfect vacuum. It equals gauge pressure plus atmospheric pressure.
5. Does pipe length increase static pressure?
No. Only vertical elevation changes static pressure. Pipe length can increase friction loss during flow.
6. Why does seawater create more pressure?
Seawater is denser than freshwater. The same depth therefore produces slightly greater hydrostatic pressure.
7. Can this calculator estimate household plumbing pressure?
It can estimate static pressure and simple losses. Actual plumbing pressure also depends on flow, pipe condition, valves, and supply behaviour.
8. Can pressure become negative?
Gauge pressure can be negative below atmospheric pressure. Absolute pressure cannot physically fall below zero.
9. Why include a safety margin?
A safety margin supports conservative planning. Final designs must still follow applicable engineering codes and equipment ratings.