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Gallons Per Minute Calculator

Calculate GPM flow rate from volume and time. Convert between gallons per minute, liters per minute, and more.

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What is a Gallons Per Minute Calculator?

A gallons per minute (GPM) calculator determines water flow rate from a known volume and the time it takes to flow. GPM is used for showerheads, garden hoses, pool pumps, fire hydrants, and plumbing design. Enter volume and time to get instant flow rate results in GPM and other units.

How to Use This Calculator

  1. Enter the volume of water that flowed.
  2. Select the volume unit (gallons, liters, cubic feet, or cubic meters).
  3. Enter the elapsed time and select the time unit.
  4. Choose how you want the flow rate displayed.
  5. Read the GPM result and conversion details instantly.

GPM Formula

The flow rate formula is:

$$\text{GPM} = \frac{\text{Volume (gallons)}}{\text{Time (minutes)}}$$

To measure GPM manually, time how long it takes to fill a container of known volume. Divide gallons by minutes. For example, 50 gallons in 5 minutes equals 10 GPM.

Related tools: Detention Time Calculator, Pool Water Maintenance Calculator, and Fire Flow Calculator.

Frequently Asked Questions

How many GPM does a shower use?

Standard US showerheads flow about 2 GPM. Water-saving models are capped at 2 GPM maximum. Older showerheads may use 2.5 to 5 GPM.

How do I calculate gallons per minute?

Fill a bucket of known volume, time how many seconds it takes, convert volume to gallons, convert time to minutes, then divide volume by time. GPM = gallons ÷ minutes.

How many GPM is a garden hose?

A typical garden hose delivers 9 to 17 GPM depending on hose diameter, length, and water pressure. Shorter, wider hoses at higher pressure produce higher flow rates.

How do I convert GPM to LPM?

Multiply GPM by 3.78541 to get liters per minute (LPM). For example, 10 GPM equals approximately 37.85 LPM.

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