Enter the plot size and how many millimetres of water you want to apply. The tool gives the water in litres and cubic metres, the application rate of your system, and how long to leave it running. Drip mode works the rate out from emitter flow and spacing; the direct mode takes a precipitation rate you already know.
1 mm = 1 litre per m². Rainfall is measured the same way.
Enter the area and the irrigation depth to see the water and run time.
How it works
One millimetre of water over one square metre is exactly one litre, which makes the whole calculation simple: litres = mm × m², and 1 mm over a hectare is 10 m³. So a 25 mm irrigation on one hectare is 250 m³ of water, no matter what equipment applies it.
The same identity turns emitter flow into an application rate. A dripper spaced 30 cm along lines 100 cm apart serves a 0.3 m² cell, so there are 3.33 emitters per m²; at 2 l/h each, the system delivers 6.67 litres per hour onto every square metre — that is 6.67 mm/h. Run time is then simply the depth divided by the rate: 10 mm at 6.67 mm/h is an hour and a half.
For sprinklers and reels the manufacturer or your own catch-can test gives a precipitation rate in mm/h directly, so switch to the direct mode and enter it. Comparing that rate against your soil’s infiltration rate matters: applying water faster than the soil can absorb it causes runoff, no matter how correct the total is. Areas can be entered in square metres, ari or hectares.
Practical examples
A 5-ar garden on drip
500 m² with a 10 mm application needs 5,000 litres, or 5 m³. With 2 l/h drippers at 30 cm on lines 1 m apart the rate is 6.67 mm/h, so the run time is 1 h 30 min and each of the roughly 1,667 emitters delivers 3 litres.
A hectare under a sprinkler
A 25 mm irrigation over one hectare is 250 m³. At a precipitation rate of 8 mm/h the set has to run 3 h 8 min in one position.
Doubling the emitter flow
Swapping 2 l/h drippers for 4 l/h at the same spacing doubles the rate to 13.3 mm/h and halves the run time to 45 minutes — the total water applied is unchanged.
A greenhouse bed of 250 m²
A lighter 7.5 mm dose on 250 m² is 1,875 litres. On the same drip layout that is 1 h 8 min of watering.
Frequently asked questions
Why is 1 mm of water 1 litre per m²?
Because a millimetre is a thousandth of a metre: 0.001 m × 1 m² = 0.001 m³, and a cubic metre is 1,000 litres. It is the reason rainfall and irrigation are both measured in millimetres — the figure is independent of area.
How many cubic metres is one millimetre per hectare?
Ten. A hectare is 10,000 m², so 1 mm is 10,000 litres, which is 10 m³. This shortcut is worth remembering when sizing a reservoir or a pump.
How do I find my system’s application rate?
For drip, the tool derives it from emitter flow and the two spacings. For sprinklers, place several straight-sided containers across the wetted area, run for a measured time, and average the depth collected — that catch-can test gives mm/h more honestly than any catalogue.
What irrigation depth should I apply?
That depends on crop stage, soil type and how much water the soil already holds. Light sandy soils take smaller, more frequent doses; heavier soils hold more per application. The tool converts the depth you choose — it cannot decide it for you.
Does the emitter spacing include the distance between lines?
Yes, both matter. Emitter spacing is the distance along one drip line, line spacing is the distance between lines. Together they define the ground area one emitter serves, and hence the rate.
What if my drip lines follow crop rows rather than a grid?
Enter the row spacing as the line spacing. If one line serves two crop rows, use the distance between lines, not between plants — the calculation is about wetted ground, not plant count.
Can I water faster to save time?
Only up to the soil’s infiltration rate. Beyond it, water runs off or ponds instead of soaking in, so the crop gets less than the numbers suggest. Splitting a large dose into two shorter runs is usually better than one long, fast one.
Does the tool account for evaporation or irrigation efficiency?
No. It reports the water delivered by the emitters. Sprinklers lose a noticeable share to wind and evaporation, and if you want to compensate you should raise the depth deliberately rather than expect a hidden factor.
How is the run time displayed?
In whole hours and minutes, rounded to the nearest minute. For very short doses the hour part disappears and only minutes are shown.
Can I use it to check my water bill or a pump’s duty?
Yes — the total in cubic metres is exactly what a meter counts. Divide the total litres by your pump’s flow in litres per hour to see how long it must run, which is often the binding constraint on a small system.
Does it work for rainfall too?
The same arithmetic applies. Entering 12 mm and your plot area tells you how much water a 12 mm shower actually delivered, which is useful when deciding whether to irrigate.
Is my data uploaded?
No. Everything is computed locally in your browser.
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