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Pool volume calculator
Pick a size or a shape, enter length, width and both depths, and get gallons and liters. The result saves on this device for the chemical calculator.
Free, no sign-up. Updated October 14, 2026.
1Start from a common size1 of 3
2Shape and units2 of 3
3Measure the water3 of 3
Measure to the water line, not the top of the wall. Same depth everywhere? Enter it in both depth boxes.
How it works
Surface area × average depth × 7.48.
Every shape uses the same idea. Only the surface area formula changes.
How to measure your pool
Measure the water, not the deck. Take length and width at the water line, and depth from the water surface to the floor. Most pools are filled a few inches below the coping, so measuring to the top of the wall overstates the volume.
- Rectangle: the longest length and the width.
- Round: straight across the middle. That is the diameter.
- Oval: the longest length and the widest width.
- Kidney or freeform: the overall length, the width across the wide end (A) and the width across the narrow end (B).
- Depth: the shallow end and the deep end. Most above-ground pools are one depth, so enter the same number twice.
The formulas
Surface area × average depth gives cubic feet, and one cubic foot holds 7.48 US gallons. Average depth is (shallow + deep) ÷ 2.
- Rectangle: length × width × average depth × 7.48.
- Round: diameter × diameter × 0.785 × average depth × 7.48. The 0.785 is π ÷ 4, which turns a diameter squared into the area of a circle.
- Oval: length × width × 0.785 × average depth × 7.48.
- Kidney or freeform: 0.45 × (width A + width B) × length × average depth × 7.48. The 0.45 is an industry approximation for curved shapes.
- Metric: cubic meters × 1,000 = liters. One US gallon is 3.785 liters.
Worked example: a 16×32 ft rectangle running from 3.5 ft to 8 ft averages 5.75 ft deep. 16 × 32 × 5.75 = 2,944 cubic feet, and 2,944 × 7.48 ≈ 22,000 gallons.
Typical pool sizes
- 12×24 ft rectangle, 3 to 5 ft deep: about 8,600 gallons.
- 16×32 ft rectangle, 3.5 to 8 ft deep: about 22,000 gallons.
- 20×40 ft rectangle, 3.5 to 8 ft deep: about 34,400 gallons.
- 24 ft round above-ground, 4.5 ft of water: about 15,200 gallons.
- 15×30 ft oval, 4 to 6 ft deep: about 13,200 gallons.
A result far from a pool of similar size usually means depth was entered in a different unit from length, or the wall height was entered instead of the water depth.
Getting a more exact number
The formulas assume the floor slopes evenly from shallow to deep. Pools with a long flat shallow section and a short, steep hopper hold less than that. For those, measure depth at four evenly spaced points along the length and average all four.
The water meter gives the real figure. Read it before a refill or before topping up a known number of inches, and read it again after. The difference is the volume of that water, which you can scale to the full depth.
What to do with your number
Chemical labels are written per 10,000 gallons, so a 22,000 gallon pool needs 2.2 times the label dose. The pool chemical calculator does that scaling and picks up the volume you calculated here on the same device. Write the number inside the equipment pad lid or on the test kit box.
Volume also sets filter turnover. Divide gallons by your pump's flow in gallons per minute to get the minutes one full turnover takes. Run the pump long enough for at least one turnover a day.
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FAQ
Questions? Glad you asked.
How many gallons is a 16×32 pool?
A 16×32 ft rectangular pool that goes from 3.5 ft in the shallow end to 8 ft in the deep end averages 5.75 ft deep, so it holds about 16 × 32 × 5.75 × 7.48 ≈ 22,000 gallons. A shallower 3 ft to 6 ft version holds about 17,200 gallons.
How do I calculate pool volume with a shallow and deep end?
Average the two depths: add the shallow and deep measurements and divide by 2. Then multiply the surface area by that average depth and by 7.48 to get gallons. This assumes the floor slopes evenly; pools with a long flat shallow area and a short steep hopper hold a little less.
How many gallons is a round above-ground pool?
Multiply the diameter by itself, then by 0.785, the average depth, and 7.48. A 24 ft round pool filled to 4.5 ft holds about 15,200 gallons; an 18 ft round at 4 ft holds about 7,600 gallons.
How accurate is a pool volume calculator?
For rectangles and rounds with even slopes it is usually within about 5 to 10 percent. Kidney and freeform pools are less exact because the 0.45 shape factor is an approximation. If you want a precise number, note your water meter reading before and after a refill.
Why does pool volume matter?
Every chemical dose is based on volume. If you guess 15,000 gallons and the pool really holds 22,000, every dose will be about a third too weak, so you chase readings that never settle. Overestimating volume does the opposite and risks overdosing.