Irrigation Water Calculator
Convert an irrigation depth into total water volume for a field, including an application-efficiency allowance.
Irrigation water workspace
Water depth × area
The underlying volume is area multiplied by water depth. The calculator treats the entered depth as the net target and divides by application efficiency to estimate gross applied water. It then converts the volume to litres, cubic metres, US gallons and acre-feet.
USDA references define one acre-foot as roughly 325,851 gallons and use acre-feet per acre as a common irrigation application measure.
Source: USDA Economic Research Service — Irrigation & Water Use.
Frequently asked questions
How much water is one acre-foot?
USDA ERS reports 1 acre-foot as about 325,851 US gallons.
What is application efficiency?
It is the share of applied water that effectively contributes to the target soil or crop-zone water amount. The calculator divides net need by efficiency to estimate gross applied water.
Can I use millimetres and hectares?
Yes. The tool supports inches or millimetres for depth and acres, hectares or square metres for area.
Does this determine when I should irrigate?
No. It converts a chosen depth and area into water volume. Irrigation scheduling should use crop, soil, weather and local guidance.