What size pump do I need?

Enough flow to turn the water over in your target time — for 20,000 gal in 8 hours, about 42 GPM. Then confirm your filter and plumbing can handle that flow.

Bigger pump = cleaner pool?

Not necessarily. Too much flow exceeds filter and pipe ratings and wastes power. Right-size it.

Home › Pool Pump Flow Rate Calculator

Pool Pump Flow Rate Calculator

Sizing a pump? Enter your volume and how fast you want a turnover, and we'll give you the flow rate to look for.

Balance your whole pool at once →Enter all your readings on one screen and get an ordered dosing plan — the full Water Report.

How to use it

Enter your pool volume.
Set your target turnover time (8 hours is common).
Match or exceed the resulting GPM at your plumbing's real flow, and check your filter can handle it.

Don't oversize the pump

A pump that pushes more GPM than your pipes and filter are rated for wastes energy and can damage the filter. Aim for the flow that gives a reasonable turnover, and make sure your filter's max flow rating is above it. Variable-speed pumps let you run low and slow for efficiency.

Frequently asked questions

What size pump do I need?: Enough flow to turn the water over in your target time — for 20,000 gal in 8 hours, about 42 GPM. Then confirm your filter and plumbing can handle that flow.
Bigger pump = cleaner pool?: Not necessarily. Too much flow exceeds filter and pipe ratings and wastes power. Right-size it.

Related calculators

Built & reviewed by a working pool-service pro. Target ranges follow CDC MAHC, PHTA, and Taylor guidance. Doses are starting estimates — add a little less than the max, re-test, and confirm against your product label. Educational tool, not a substitute for a water test or professional advice.