GPM Calculator
Calculate gallons per minute (GPM) flow rate for pipes, pumps, pools, and irrigation systems. Multiple calculation methods supported including pipe velocity, volume/time, and container fill.
GPM Calculator
Pipe Flow Rate
Typical: 2-10 ft/s for water supply
Understanding GPM Flow Rate
GPM (Gallons Per Minute) is a standard unit for measuring volumetric flow rate. It tells you how many gallons of liquid pass through a point in one minute. Understanding GPM is essential for designing plumbing systems, sizing pumps, planning irrigation, and maintaining pool filtration systems.
Calculation Methods
Pipe + Velocity
Calculate GPM from pipe diameter and water velocity. Best for estimating flow in existing pipes.
Volume + Time
Measure volume collected over time. Most accurate for actual flow measurement.
Container Fill
Time how long to fill a known container. Simple field measurement method.
Common GPM Requirements
- Household Supply: 6-12 GPM for 3/4" to 1" lines
- Pool Filtration: Turnover rate of 8-12 hours requires 40-80 GPM for average pools
- Sprinkler Systems: 1-20 GPM per zone depending on coverage
- Irrigation: 5-15 GPM per acre for agricultural use
- Fire Protection: 250+ GPM for commercial systems
Recommended Water Velocities
- General Plumbing: 3-8 ft/s
- Pump Suction Lines: 2-4 ft/s (avoid cavitation)
- Pump Discharge: 4-10 ft/s
- Hot Water: 3-5 ft/s (reduce noise)
Unit Conversions
This calculator automatically converts GPM to other common flow rate units:
- Liters per Minute (L/min): GPM × 3.78541
- Liters per Hour (L/hr): GPM × 227.125
- Cubic Feet per Minute (CFM): GPM ÷ 7.48052
- Cubic Meters per Hour (m³/hr): GPM × 0.2271