Garden Watering Calculator

Estimate how much water your garden needs each week and how long to water with a hose, drip line, sprinkler, or irrigation system. Calculate gallons needed, rainfall adjustment, watering sessions, run time, and estimated water cost.

Calculate Garden Watering

1 inch of water over 1 square foot = 0.623 gallons.
Your result will appear here.

How the garden watering calculator works

Garden area mode:
The calculator uses garden area, weekly water depth, rainfall, and efficiency to estimate gallons needed.

Raised bed mode:
The calculator multiplies bed area by the number of beds and adjusts water needs for rainfall and conditions.

Container mode:
The calculator uses the number of containers and gallons per container per watering to estimate weekly water needs.

Run time mode:
The calculator estimates how long to water based on gallons needed and system flow rate.

Why use a garden watering calculator?

A garden watering calculator helps estimate how much water your garden needs and how long to run your irrigation system.

It can help avoid overwatering, underwatering, wasted water, dry raised beds, inconsistent container watering, and unclear irrigation run times.

What your result means

Your result shows weekly gallons needed, gallons per watering session, irrigation run time, monthly gallons, estimated water cost, rainfall adjustment, efficiency adjustment, and water depth needed after rainfall.

Garden watering formulas

Frequently asked questions

How much water does a garden need per week?

Many gardens use about 1 inch of water per week as a starting estimate, but actual needs vary by crop, soil, heat, wind, rainfall, mulch, and plant maturity.

How many gallons is 1 inch of water over 1 square foot?

One inch of water over one square foot is about 0.623 gallons.

How do I calculate watering time?

Divide gallons needed per watering session by your hose, drip, sprinkler, or irrigation system flow rate in gallons per minute.

Should rainfall be subtracted from watering needs?

Yes. Rainfall helps meet part of the weekly water requirement. Subtract rainfall from the target weekly water depth before calculating irrigation water.

Is this garden watering calculator exact?

No. This is an estimate. Actual watering needs can vary by plant type, soil texture, mulch, drainage, weather, wind, sun exposure, irrigation pattern, and local conditions.