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Pump Flow Rate Calculator

Convert a pump's flow between litres per minute, litres per hour, m³/h and gallons, and see how long a tank takes to fill.

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Inputs

Formula

  • 1 m³/h = 16.67 litres/min
  • Fill time = tank ÷ flow
  • Daily output = flow × 60 × hours

Pump makers quote flow in different units — lpm on the nameplate, m³/h in catalogues, gpm on imported pumps. This tool converts between them and shows how the flow translates into real filling times and daily water delivery.

Step-by-step calculation

  1. 1

    Per hour

    lpm × 60

    3,600 L/h

  2. 2

    Fill time

    tank ÷ flow

    16.67 min

Worked example

  1. 1A 60 lpm pump = 3.6 m³/h = 15.9 US gpm.
  2. 2A 1,000 litre tank fills in 1,000 ÷ 60 = 16.7 minutes.
  3. 3Running 2 hours a day delivers 7,200 litres.

Tips

  • Flow drops as head increases — check the pump curve at your actual lift.
  • Measure real flow with a bucket and stopwatch; nameplate values are best-case.

Frequently asked questions

How many litres per minute is 1 HP?

There is no fixed answer — it depends on head. A 1 HP domestic pump gives roughly 60–100 lpm at 15 m head.

How do I convert lpm to m³/h?

Divide by 16.67. So 100 lpm is 6 m³/h.

Why does my pump deliver less than rated?

Higher lift, narrow pipes, bends and a partly clogged foot valve all cut the flow.

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