Pool Pump Size Calculator
Find the right pump size in GPM and HP for your pool based on volume, turnovers, and pipe specifications.
gallons
per day
hrs/day
feet
How to Size a Pool Pump
The goal of a pool pump is to turn over the entire pool volume at least once — ideally twice — per day. The required flow rate in GPM is calculated as: GPM = (Pool Volume × Turnovers) ÷ (Operating Hours × 60).
Pipe diameter matters: smaller pipes create more friction (head loss), requiring a more powerful pump. A 1.5-inch pipe at 40 GPM generates significantly more resistance than a 2-inch pipe at the same flow rate.
Recommended Pump HP by GPM
- Under 40 GPM — 0.5 HP
- 40–60 GPM — 0.75 HP
- 60–80 GPM — 1 HP
- 80–100 GPM — 1.5 HP
- Over 100 GPM — 2 HP
These are baseline guidelines. Always account for additional head loss from filters, heaters, cleaners, and elevation changes. Consult the pump manufacturer's performance curve for your specific installation.