Hydrostatic Pressure Calculator
Water pressure by depth with gauge and absolute readouts.
What it does
Water weight stacks with depth. Ten meters of fresh water adds about 98 kilopascals gauge, nearly one extra atmosphere. Gauges read that water column alone, absolute adds the air above.
The tool above takes depth and returns gauge, absolute, and small depth. The defaults 10 m match the worked example, so the page opens showing 98.07 kPa gauge. Switch to imperial for feet and psi.
Metric gauge is 1000 x 9.80665 x depth in pascals. Absolute adds 101325. Imperial gauge is 62.4 pounds per cubic foot times feet for psf, over 144 for psi, plus 14.696 for absolute. A 32.8 ft column mirrors 10 m at 14.21 psi gauge.
Fresh water at standard gravity is assumed. Salt runs about 2.5 percent higher, altitude lowers air add. Tanks with air caps add their own head beyond water column.
This page shows the formulas, one full hand checked example at 10 m, a reference table, and practice checks that run through the tool in both unit systems.
How to use
- Pick Metric (m, kPa) or Imperial (ft, psi).
- Type depth below the surface.
- Read Gauge as water column only.
- Read Absolute with air added.
- Use gauge for burst and structure, absolute for gas laws.
- Add tank air head separately if pressurized.
Formula
- rho
- 1000 kg/m3 fresh water, 62.4 lb/ft3 imperial.
- g
- 9.80665 m/s2.
- air
- 101.325 kPa or 14.696 psi added for absolute.
Gauge zero at the surface. Salt water near 1025 kg/m3 reads higher. Altitude drops the air add.
Worked example
Example: 10 m fresh water
Find gauge and absolute ten meters down.
- Gauge: 1000 x 9.80665 x 10 = 98066.5 Pa.
- Kilo: 98.07 kPa gauge.
- Air: 101.325 kPa.
- Absolute: 98.07 + 101.325 = 199.39 kPa.
- Small depth: 1000 cm.
- Imperial mirror 32.8 ft gives 14.21 psi gauge.
Reference table
| Depth | Gauge | Absolute |
|---|---|---|
| 0 m | 0 kPa | 101.33 kPa |
| 5 m | 49.03 kPa | 150.36 kPa |
| 10 m | 98.07 kPa | 199.39 kPa |
| 32.8 ft | 14.21 psi | 28.91 psi |
Limits
- Fresh water only. Salt reads higher.
- Still water assumed. Flow adds dynamic terms.
- Standard g and air used.
- No tank air cap here.
Common mistakes
- Reading gauge as absolute without air.
- Mixing feet with meters in rho g h.
- Using salt rho for fresh math without noting.
- Forgetting psf to psi divide by 144.
- Adding air twice.
Try it yourself
Quick checks. Answers sit tucked under each question.
5 m?
Gauge 49.03 kPa, absolute 150.36 kPa.
0 m?
Gauge 0 kPa, absolute 101.33 kPa.
Questions
10 m gauge?
98.07 kPa.
Absolute?
Gauge plus air. Here 199.39 kPa.
psi per foot?
About 0.433 psi per foot fresh.
Salt?
Near 2.5 percent higher.
Altitude?
Lowers air add.
Gauge zero?
At the surface.