Pool Filter Sizing Calculator
Estimate the flow capacity your pool filter should support based on pool volume and desired circulation time. Use the result as a starting point when comparing cartridge, sand, and DE filters for your pool system.
Calculate Your Required Filter Flow
Estimate the flow capacity your pool filter should support based on pool volume and your selected circulation time.
Your Estimated Requirements
Your pool needs an estimated average flow of 31.3 GPM for an eight-hour circulation period. An illustrative 25% planning margin increases that figure to 39.1 GPM.
Compare these figures with manufacturer flow ratings for the specific filter. Check pump performance, plumbing resistance and filter specifications before selecting equipment. The 25% margin is not a universal manufacturer sizing requirement.
How the Pool Filter Sizing Calculator Works
The calculator estimates the average flow rate needed to move the entered pool volume during your selected circulation period.
Pool Volume ÷ Circulation Time in Minutes = Required Average GPM
For example, circulating 15,000 gallons over eight hours requires an average flow rate of about 31 gallons per minute.
If you do not know your pool's water volume, use the Pool Volume Calculator first.
A second result adds a 25% planning margin to the calculated flow rate. This margin is provided as a comparison aid and is not a manufacturer sizing requirement.
Filter square-foot ratings should not be compared directly between cartridge, sand, and DE filters because the filtration media and designs are different. Instead, compare the calculated flow requirement with the rated flow capacity and specifications of the particular filter being considered.
For more detail on matching filter capacity to a pool, see How Big Should My Pool Filter Be?
If you're still deciding which filtration technology to use, our Cartridge vs. Sand vs. DE Pool Filters comparison explains the major differences between the three types.
Actual system flow can also be affected by plumbing size, pump performance, filters, heaters, valves, cleaners, water features, and other equipment.
Because pump and filter sizing are closely related, you can also use the Pool Pump Sizing Calculator to estimate the circulation flow your pump needs to provide.
For more information about filter types, sizing, maintenance, pressure, and performance, see our Complete Guide to Pool Filters.
Once you know the approximate flow capacity your system requires, compare available pool filters while checking the manufacturer's rated flow, filter type, plumbing connections, and sizing requirements for the exact model.