GPM Calculator

Calculate gallons per minute from water volume and time, convert GPM to gallons per hour, liters per minute, cubic feet per minute, estimate fill time, total water use, fixture demand, and monthly water cost.

Calculate GPM

GPM = Gallons ÷ Minutes.
Your result will appear here.

How the GPM calculator works

Gallons and time:
The calculator divides gallons by minutes to estimate gallons per minute.

GPM and time:
Enter a known GPM and run time to estimate total gallons used.

Gallons and GPM:
Enter gallons and flow rate to estimate fill time or drain time.

Fixture demand:
Enter fixture count, GPM per fixture, and simultaneous use percentage to estimate total demand.

Why use a GPM calculator?

A GPM calculator helps estimate how fast water flows from a faucet, shower, hose, pipe, tank, or irrigation outlet.

It can help compare gallons per minute, gallons per hour, liters per minute, total gallons, fill time, daily use, monthly use, and estimated water cost.

What your result means

Your result shows estimated gallons per minute, gallons per hour, liters per minute, total gallons, fill time, fixture demand, daily water use, monthly water use, and estimated water cost. These are planning estimates only. Actual GPM can vary based on pressure, pipe size, hose size, fixture restrictions, valves, filters, elevation, and plumbing layout.

GPM formulas

Frequently asked questions

How do you calculate GPM?

Divide the total gallons by the number of minutes. For example, 10 gallons in 2 minutes equals 5 GPM.

What does GPM mean?

GPM means gallons per minute. It tells you how many gallons of water flow each minute.

How do you calculate fill time from GPM?

Divide the total gallons needed by the GPM flow rate. The result is the estimated fill time in minutes.

Is this GPM calculator exact?

No. This calculator gives an estimate. Actual flow can change due to water pressure, pipe size, hose size, valves, fittings, filters, elevation, and fixture restrictions.