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Pressure Measurement · Glossary

What is Pressure Head?

Symbol: hm, mWC, ftPressure Measurement

Pressure head is pressure expressed as the height of a liquid column that would produce it.

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Pressure Head Explained

Pumps are rated in head because head does not depend on the liquid density: a pump gives the same head on water or oil, but different pressure.

Low pressures are often stated as mm or inches of water column (mmWC, inH₂O).

Pressure Head Formula

h = p ÷ (ρ × g)
hhead (m)
ppressure (Pa)
ρdensity (kg/m³)
Example: 1 bar of water (1000 kg/m³) is 100,000 ÷ (1000 × 9.80665) ≈ 10.2 m.
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Calculators for Pressure Head

CalculatorHydrostatic Pressure CalculatorFree online calculator with formula and worked example.CalculatorPump Power CalculatorFree online calculator with formula and worked example.CalculatorNPSH Available CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Pressure Head?

Pressure head is pressure expressed as the height of a liquid column that would produce it.

Why do pump curves use head?

Head is independent of density, so one curve works for any liquid with similar viscosity.

What is 1 inH₂O in pascals?

About 249 Pa, depending on the reference water temperature used.

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More Pressure Measurement Terms

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All pressure measurement terms · Full glossary A to Z

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