Pool Pump Size Calculator
Enter your pool volume and a turnover time to get the flow rate in GPM your pump needs, and enter a pump's flow to see how long it takes to turn the water over once.
Flow needed to turn over once in 8 hours
31 GPM
This is within the range of standard 1.5-inch pool plumbing.
Already have a pump?
Enter its flow rate to see how long it takes to turn the water over once.
The standard target is turning your whole pool volume over in about 8 hours, so flow needed equals volume divided by (hours times 60). Bigger is not better: a pump that outruns your filter or plumbing wastes energy and filters poorly. A variable-speed pump hits this flow slowly and cheaply, which is why they have become the default.
Flow, not horsepower
Pumps are sold by horsepower, but what matters is flow in GPM and whether your filter and plumbing can handle it. Start from an accurate pool volume, match the flow to your turnover goal, and pick the pump from there. Choosing the pump itself? See best pool pumps and best pool filters.
Frequently asked questions
What size pump do I need for my pool?
Size the pump by the flow it needs to turn your pool's full volume over in about 8 hours. Flow needed in gallons per minute equals your volume divided by the turnover time in minutes. A 15,000 gallon pool on an 8 hour turnover needs about 31 GPM. Keep that flow within your filter's and plumbing's limits.
What is pool turnover?
Turnover is the time it takes the pump to circulate your entire pool volume through the filter once. The common target is one turnover in about 8 hours, though many pools do fine with a turnover or two spread across a day, especially with a variable-speed pump running long and slow.
Is a bigger pool pump better?
No. A pump that pushes more water than your filter or plumbing can handle wastes energy, raises pressure, and filters worse because water moves through the filter too fast. Match the flow to your turnover goal and your filter's rating, and use a variable-speed pump to hit it efficiently.
How many hours should I run my pool pump?
Long enough to turn the water over about once a day, which depends on your pump's flow and your pool size. Enter your pump's GPM above to see the hours for one turnover. Variable-speed pumps often run many hours at low speed, which is quieter and cheaper than a single-speed pump running fewer hours.