Pool Volume Calculator
Gallons or liters, water weight, and surface for rectangular and round pools.
What it does
Pool chemistry, pumps, heaters, and covers all start from water volume. Rectangular pools multiply length by width by average depth, while round pools use pi times radius squared times depth. Average depth handles the common slope from shallow to deep end.
The tool above covers both shapes in imperial or metric. It returns volume, water weight, and surface area for covers and heating.
Chemical dosing follows volume directly. Chlorine, salt, and pH products all quote per ten thousand gallons or per cubic meter, so an honest volume keeps dosing safe and cheap.
Weight surprises owners most. The example pool below carries eighty tons of water, which is why above ground pools need level compacted bases and rooftop installations need engineers, not guesses.
How to use
- Switch the unit system first: imperial for feet and gallons, metric for meters and liters.
- Pick rectangular or round shape.
- Measure length, width, or diameter at the waterline.
- Average shallow plus deep ends divided by two for depth.
Formula
- avg depth
- (Shallow + deep) / 2 for sloped floors.
- 7.48052
- US gallons per cubic foot.
- 8.34 lb
- Weight per gallon for the tons math.
Steps, benches, and swimouts displace a little water that this math counts. The error runs low single percents on home pools.
Worked example
Example: 32 x 16 ft pool, 5 ft average depth
Rectangular pool 32 by 16, average depth 5 ft.
- Volume: 32 x 16 x 5 = 2,560 ft3.
- Gallons: 2,560 x 7.48052 = 19,150 gal.
- Weight: 19,150 x 8.34 lb = 159,711 lb, which is 79.9 tons.
- Surface: 32 x 16 = 512 ft2 for the cover.
Reference table
| Pool | Volume | Weight |
|---|---|---|
| 24 ft round, 4 ft deep | about 13,500 gal | about 56 tons |
| 32 x 16 ft, 5 ft avg | 19,150 gal | 79.9 tons |
| 40 x 20 ft, 5.5 ft avg | about 32,900 gal | about 137 tons |
| 25 m x 12.5 m, 2 m (Olympic training) | 625 m3 | 625 tonnes |
Limits
- Box and cylinder shapes. Kidneys and lagoons need section math.
- Steps and benches ignored, small error.
- Fresh water assumed. Salt adds a little density.
- Heating and pump sizing need turnover rates too.
Common mistakes
- Using deep end depth for the whole pool.
- Measuring the deck instead of the waterline.
- Dosing chemicals off guessed gallons.
- Forgetting water weight on structures.
- Filling past the skimmer middle and killing circulation.
Try it yourself
Quick checks. Answers sit tucked under each question.
20 x 10 ft pool, 4 ft average. Gallons?
20 x 10 x 4 = 800 ft3. Then 800 x 7.48052 = 5,984 gal.
10 x 5 m pool, 1.5 m deep. Volume?
10 x 5 x 1.5 = 75 m3, which is 75,000 liters.
Questions
How many gallons in my pool?
Length times width times average depth in feet, times 7.48. A 32x16x5 pool holds 19,150 gallons.
How do I average the depth?
Add shallow and deep ends and halve. Three and seven feet average five.
Why does volume matter?
Chemicals dose per volume. Wrong gallons mean algae or bleached liners.
How heavy is pool water?
8.34 lb per gallon. Home pools weigh tens of tons, which structures must carry.
Round pool formula?
Pi times radius squared times depth, then 7.48 for gallons.
How often to turn the water over?
Most residential systems aim the full volume through the filter every 6 to 8 hours.