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Pump Head Basics

Understand pump head as energy per unit weight and how differential pressure converts to equivalent liquid head.

Referencefluids & pipingPublishedLast reviewed: 2026-05-16

Use pump head to compare pressure measurements, pump curves, and system losses in a form that is tied to fluid energy rather than one pressure unit.

What This Means

Pump head is energy added per unit weight of liquid, expressed as a length of fluid. A pressure rise can be converted to head using density and gravity.

The same pressure rise represents different head for different fluid densities. Likewise, the same head represents different pressure rise for water, oil, or another liquid.

Key Formula

H = Delta p / (rho g)
Delta p = rho g H
  • H is equivalent liquid head.
  • Delta p is pump differential pressure or pressure rise.
  • rho is liquid density.
  • g is gravitational acceleration.

Use This When

  • Converting a pump discharge-minus-suction pressure reading into equivalent head.
  • Comparing a simple pressure measurement with a pump curve.
  • Checking whether a calculated pipe head loss is in the same range as available pump head.
  • Communicating pump performance in feet or meters of liquid.

Assumptions

  • The pressure input is a differential pressure across the pump or system section.
  • Liquid density is constant over the conversion.
  • Velocity-head and elevation differences are either negligible or handled separately.
  • The calculation is for liquids, not gas compression.

Limitations

  • Pressure-to-head conversion is not a complete pump selection.
  • Total dynamic head can include static elevation, velocity-head changes, pipe losses, fittings, valves, and equipment losses.
  • NPSH, cavitation margin, efficiency, and pump curve selection require additional methods and manufacturer data.
  • Gauge pressure from a single location is not enough to determine pump differential head.

Common Mistakes

  • Using discharge gauge pressure alone as pump head.
  • Comparing pump head to pressure without converting for fluid density.
  • Ignoring suction pressure, elevation, or system losses.
  • Treating pressure head as total dynamic head.
  • Applying liquid pump-head relationships to gas compressor sizing.

Sources

This reference is based on Crane TP-410 for pump-system head and pressure/liquid-head conversion context, with White's Fluid Mechanics used for pressure head and pump-head relationships.