Construction

Instant, private, and free

Gallons per Minute Calculator.

Calculate flow rate from gallons and elapsed minutes.

On-device calculationNo signup
01

Set your values

Results update as you type.

gallons: 100

gallons

0.0000
minutes: 5

minutes

0.0000
Gallons/minute: 20

Gallons/minute

0.0000
Liters/minute: 75.7082

Liters/minute

0.0000

Planning arithmetic only; enter explicit dimensions, areas, and elapsed times. No code, product, density, or design recommendation is inferred.

Use Cases

Check pump performance

Measure how many gallons a pump delivers in a set time to verify it meets specifications.

Example: If a pump fills a 50-gallon tank in 2 minutes, it flows 25 GPM.

Size irrigation systems

Determine the flow rate of a water source to plan sprinkler or drip systems.

Example: A hose fills a 5-gallon bucket in 30 seconds (0.5 min) → 10 GPM.

Frequently Asked Questions

How do I calculate gallons per minute?
Enter the total gallons of liquid and the elapsed time in minutes. The calculator divides gallons by minutes to give you the flow rate in GPM.
What units does this calculator use?
It uses gallons (gal) for volume and minutes (min) for time. The result is in gallons per minute (GPM).
Can I use this for any liquid?
Yes, as long as you measure the volume in gallons and time in minutes, the calculator works for water, oil, or other liquids.

Tips & Common Mistakes

Tips

  • Use a stopwatch for accurate time measurement.
  • Ensure the container is fully drained or filled to get precise gallon readings.
  • For continuous flow, measure over a longer period to average out fluctuations.
  • Convert seconds to minutes by dividing by 60 before entering.

Common Mistakes to Avoid

  • Forgetting to convert seconds to minutes, leading to incorrect GPM.
  • Using a container with an unknown volume instead of a calibrated one.
  • Not accounting for start/stop time errors when measuring manually.

Last updated: August 13, 2026