Rolling green paddocks in soft evening light
Handy tools

Irrigation calculator

How many millimetres did that run put on? Turn your pump flow and hours into megalitres and mm - and see how long to run for the depth you want.

The paddock or the part of it under the sprinklers. 1 acre = 0.405 ha.

From your flow meter or pump test. 1 ML a day ≈ 11.6 L/s.

How long the pump ran, or will run.

Optional: allow for drift, evaporation and run-off. 100 to skip.

Optional: what you want to put on. 0 to skip.

Optional: your own price or pumping cost. 0 to skip.

This run puts on

12.96 mm0.51 inches
1.296 MLpumped
1.08mm an hour

Water on the paddock

12.96 mmTarget 25 mm
Hours for your target
23 h 9 min (2.5 ML)
This run vs your target
52% of your 25 mm
Megalitres per hectare
0.13 ML/ha
Lost to drift and run-off
None allowed for
Water cost at your price
Enter your own $/ML
Link to these numbers

How we work it out

  • Megalitres: L/s × 3,600 × hours ÷ 1,000,000. So 30 L/s for 12 hours is 1.296 ML.
  • Millimetres: 1 ML spread over 1 hectare is 100 mm. So 1.296 ML on 10 ha is 12.96 mm (less any efficiency allowance).
  • Hours for a target: target mm × hectares ÷ 100 = ML needed, then divided by what the pump moves in an hour.

How much water a crop or pasture needs depends on soil, weather and the season - talk to your agronomist or local irrigation adviser, and stay within your licence or allocation. This is arithmetic on your own numbers, not advice, a water price or an allocation. Nothing you type is stored or sent anywhere.

Keep track of the rain too

Log your rain gauge readings, or work out what's left in the tank or dam.

Rain gauge diary Water tank & dam calculator