Use average depth, not deepest depth
For rectangular, oval, and round pools, average depth is usually the shallow-end depth plus deep-end depth divided by two. A depth mistake can produce a big dosing mistake, so treat this as an estimate and dose in stages.
If your pool has a flat bottom, enter the same number for shallow and deep depth. If it slopes, use the shallow and deep readings from the waterline to the floor. The calculator averages those two numbers because most chemical dosing guides assume the pool volume is an estimate, not a survey-grade measurement.
Use the estimate for salt, chlorine, and stabilizer
Many chemical dosing mistakes start with the wrong gallons number. After you estimate volume here, you can send the result directly into the salt calculator with the gallons field prefilled.
Pool salt, chlorine, stabilizer, calcium hardness, pH, and alkalinity adjustments all scale with water volume. If your gallons estimate is 20% too high, the suggested chemical dose can be 20% too high too. That is why this page shows gallons and liters, plus a pump turnover estimate for planning circulation time.
Feet, meters, gallons, and liters
The calculator accepts feet or meters because pool owners often have dimensions from different sources. Builder paperwork may list meters, while pool chemical labels in the United States usually dose by gallons. When you switch to meters, the calculator converts cubic meters to US gallons and liters so you can use either label style without doing the conversion separately.
If you are measuring by hand, measure the water surface rather than the outside of the pool wall. For above-ground pools, the advertised size can be slightly different from actual water dimensions, especially when the waterline sits below the top rail. A quick real-world measurement usually beats relying on the model name alone.
Rounding is normal. A pool volume estimate does not need to be perfect for every small adjustment, but it should be close enough that a large salt, chlorine, stabilizer, or alkalinity change does not overshoot badly. When in doubt, round the dose down, circulate, and retest.
Pool volume formulas used here
Length x width x average depth x 7.48 = gallons.
3.1416 x radius x radius x average depth x 7.48 = gallons.
3.1416 x half length x half width x average depth x 7.48 = gallons.
What the 8-hour turnover number means
Turnover is the estimated flow rate needed to move a pool volume through the circulation system over a chosen period. The 8-hour GPM number is simple: gallons divided by 480 minutes. Real flow can be lower because filters, pipe length, valves, heaters, and elevation all add resistance, so treat the number as a planning estimate rather than a pump sizing guarantee.
How accurate does the pool volume need to be?
For routine chemical adjustments, a reasonable estimate is usually enough if you add in stages and retest. The risk comes from treating an estimate like a perfect number. If you are correcting salt, stabilizer, calcium hardness, or alkalinity by a large amount, use the calculator result as a first pass, add less than the full dose, circulate, and test again.
Irregular pools, tanning ledges, attached spas, beach entries, and large steps can make any simple shape formula less accurate. In those cases, use the quick surface-area mode or estimate the main body of water separately from shallow shelves, then combine the results.
Common pool size examples
These examples use average water depth, not wall height. They are useful for checking whether your result is in the right range before using the gallons number in a salt, chlorine, or stabilizer calculation.
| Pool shape and size | Average depth | Estimated gallons |
|---|---|---|
| 24 ft round | 4.5 ft | about 15,200 gal |
| 16 x 32 rectangle | 5 ft | about 19,100 gal |
| 18 x 36 rectangle | 5 ft | about 24,200 gal |
| 30 x 15 oval | 5 ft | about 13,200 gal |