Garden irrigation

Lawn Watering Calculator

Subtract effective rainfall from a locally chosen lawn dose before converting to volume.

YOUR WATER PLAN

Your result

Remaining net depth15.00 mm

Net lawn water1,500.00 L1.500 m³ · 396.26 US gal

Gross water volume1,666.67 L1.667 m³ · 440.29 US gal

Bars compare only results in the same unit group. They are normalized, not a time-series forecast.

Planning result based on your inputs.

Subtract effective rainfall from a locally chosen lawn dose before converting to volume.

V = area × max(0, target depth − effective rain)/η

The prefilled form is a worked example. Its base-unit inputs and expected outputs are shown below; use the reset button to restore it.

Input	Example
Area	100
Target net water depth	20
Effective rain for the period	5
System efficiency (separate losses)	0.9

Remaining net depth15.00 mm

Net lawn water1,500.00 L1.500 m³ · 396.26 US gal

Gross water volume1,666.67 L1.667 m³ · 440.29 US gal

How should I choose the inputs?

Use measurements and local records for the stated period. All preset values are illustrative examples, not recommendations.

What does this result leave out?

No universal weekly dose is assumed. Grass type, climate, rooting depth and local restrictions determine whether irrigation is needed.

Apply an ET?/Kc water balance for a garden hydrozone. ET? is a daily input, not calculated weather data.

Convert a chosen net application depth into gross water volume with an explicit efficiency.

Calculate nominal zone flow and delivered volume from emitter count, measured emitter flow and runtime.

Method version 1.0 · Last reviewed: 2026-10-10