Pool Pump Size Calculator
An oversized pump wastes electricity and an undersized pump cannot keep your pool clean. Enter your pool volume, desired turnover time, and plumbing details to find the right flow rate (GPM) and pump horsepower for proper filtration.
The core formula:
Required GPM = Pool Volume (gallons) / (Turnover Time (hours) x 60)
What is turnover time?
Turnover time is how long it takes the pump to circulate the entire pool volume through the filter once. Industry standard for residential pools is 8 hours. Commercial pools typically require 6 hours. The pump needs to run at least one full turnover per day.
Total Dynamic Head (TDH) explained:
- Static head -- vertical height the pump lifts water
- Friction loss -- resistance from pipe length and diameter
- Fittings loss -- elbows, valves, and connectors add resistance
- Filter resistance -- your filter creates back-pressure
Pipe size matters: Undersized pipes restrict flow and make the pump work harder. 1.5-inch pipe maxes out around 45 GPM, while 2-inch pipe handles up to 73 GPM. If your required GPM is close to the pipe maximum, consider upgrading the plumbing.
Variable speed pumps: Modern variable-speed pumps save 50-80% on electricity by running at lower speeds for longer periods. They are now required by law in many states for new installations and pool remodels.