Case 1
- Pool length
- 8m
- Pool width
- 4m
- Average depth
- 1.5m
- Turnover time
- 8h
6.00m³/h
Open with these valuesPool Pump Size Calculator
6.00m³/h
Result: 6.00 m³/hThis gives a flow rate, not a horsepower rating — which pump reaches it depends on your pipework and head, not on the pool. Turnover time is the lever: cutting it from eight hours to six raises the required flow by a third.
Worked examples
Case 2
- Pool length
- 10m
- Pool width
- 5m
- Average depth
- 1.5m
- Turnover time
- 6h
12.50m³/h
Open with these valuesCase 3
- Pool length
- 6m
- Pool width
- 3m
- Average depth
- 1.3m
- Turnover time
- 8h
2.93m³/h
Open with these valuesHow it's calculated
flow = volume ÷ turnover time
- StepSwitch the units above for gallons per minute.
- StepEnter length, width and the average depth.
- StepSet the turnover time — eight hours is the common target.
- ResultRead the flow rate and take it to the pump's own curve.
What this number means
A flow rate, not a horsepower rating
The pool sets the flow; the pipework, the filter and the head decide which motor reaches it. Take the figure from here to the pump's own curve rather than straight to a horsepower label.
Turnover time is the real lever
The result is the water volume divided by the turnover time, so the time you set moves it directly. A pool of 8 by 4 metres at 1.5 metres average depth holds 48 m³: eight hours needs 6 m³ per hour, six hours needs 8.
Eight hours is the usual target
That is the turnover time this calculator starts with. Shortening it is a decision about the installation rather than about the pool, because the volume of water stays the same.
Average depth, not the deep end
The volume uses one depth for the whole pool, so a sloping floor needs the average. Entering 2 m instead of an average of 1.5 m turns 6 m³ per hour into 8, a third more than the pool actually needs.
Commonly misread
I entered the depth measured at the deep end.
The field asks for the average depth across the whole pool. On an 8 by 4 metre pool, 2 m instead of an average 1.5 m raises the answer from 6 to 8 m³ per hour.
6 m³ per hour is the pump I go out and buy.
It is the flow the pool needs, not a figure on a box. Match it against the pump's curve at the head of your own installation.
My pool is round, so this calculator does not apply.
Only the product of length and width is ever used. Pick any pair whose product equals the actual water surface area.
I halved the turnover time and kept the same pump.
Halving the time doubles the flow the pool needs. Check the new figure against the pump's curve before assuming it still fits.
Questions
What flow rate does my pool need?
The water volume divided by the turnover time. A pool of 8 by 4 metres at 1.5 metres average depth holds 48 m³, so a turnover in eight hours needs 6 m³ per hour.
How long should a turnover take?
Eight hours is the common target and the default here. Shortening it to six raises the required flow from 6 to 8 m³ per hour — a third more for the same pool.
Why is there no horsepower rating?
Because the same flow needs a different motor depending on your pipework, filter and head. The flow rate is the property of the pool; the horsepower is a property of the installation.
What about a round or freeform pool?
Enter a length and width whose product matches the actual surface area. The calculator only ever uses the product, so any pair that gives the right area works.
Sources and last check
Information, not professional advice.