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Gurukrupa Enterprises
Pump Calculators

Pump Efficiency Calculator

Calculate pump efficiency from measured flow rate, head and shaft power.

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About this calculator

This calculator finds a pump's actual efficiency at its current operating point, from measured flow rate, head and shaft power — useful for checking a pump's performance against its rated efficiency, or diagnosing wear and performance loss.

Formula

η (%) = (Q × H) ÷ (367.3 × P) × 100
  • QFlow rate — m³/hr
  • HTotal dynamic head — metres
  • PMeasured shaft power — kW
  • ηPump efficiency — %

Worked Example

Given: A pump delivers 50 m³/hr against a 30m head, drawing 5.83 kW of shaft power.

Result: η = (50 × 30) ÷ (367.3 × 5.83) × 100 = 70.1%.

How to Use

  1. Measure or read the current flow rate in m³/hr.
  2. Measure or calculate the current total head in metres.
  3. Measure the shaft power (or motor input power divided by motor efficiency) in kW.
  4. Click Calculate to get the resulting pump efficiency.

Important Assumptions

  • Assumes water; for other liquids include specific gravity in the underlying hydraulic power calculation.
  • Efficiency found this way reflects the pump's condition and operating point at the time of measurement — it will differ at other flows and heads on the same pump.

Common Mistakes

  • Using motor electrical input power instead of pump shaft power without correcting for motor efficiency, which understates pump efficiency.

Frequently Asked Questions

Why might a pump's calculated efficiency be lower than its nameplate value?

Efficiency drops from the rated best-efficiency point as flow and head move away from design conditions, and also declines over time due to wear, impeller erosion or internal clearance increases.

Can this be used to detect a failing pump?

Yes — a noticeably falling efficiency over time at the same operating point is a common early indicator of wear, cavitation damage or impeller fouling.

These calculators are provided for informational and estimation purposes. Results depend on the assumptions and input values used. Always verify critical engineering calculations against applicable standards, manufacturer specifications, site measurements, and qualified professional advice.