Pool Volume Calculator — Measure Gallons and Refill
Measure a pool’s inside dimensions, floor zones and waterline to estimate current gallons, full capacity and refill water.
Measure the water you have
About 7,810 US gal in the pool now
A measured ½ ft drop below the intended full line leaves about 1,077 US gal to refill.
Describe the inside water space
Use horizontal lengths along the pool, not the sloped floor length. Depths are measured from the intended full waterline.
For a shelf and deep end, measure the two flat lengths and the horizontal run of the slope. The deep flat is the length left over.
12 ft shallow flat + 6 ft slope + 6 ft deep flat. The usual whole-length average-depth estimate is 9,695 US gal, about 808 US gal higher for this measured floor.
Use this volume for a salt comparison Use this volume with a measured chlorine testWhy measure the floor sections?
The familiar average of shallow and deep depth is exact when a rectangular floor slopes evenly from one end to the other. A flat shallow shelf and a flat deep section change the volume. This editor adds the three measured sections; it does not assume every pool needs a correction.
Full volume = width × [shallow flat × shallow depth + slope run × average of its end depths + deep flat × deep depth]. The deep flat is the inside length left after subtracting the shallow flat and slope run.
What does “water now” mean?
Measure how far the current waterline is below the intended full line. The drawing clips each section at that line; a partly dry shallow shelf contributes no water. “Add to full” is the difference between the two calculated volumes, not a chemical dose or a recommendation to fill above the builder’s operating line.
Round and oval modes assume a level floor. For steps, benches, curved walls, a hopper or varying width, measure smaller sections or confirm capacity with your builder. These are geometric estimates, not certified volumes.
Measurement context: Pentair pool volume calculator and Pentair engineering guide. We integrate the stated shelf/slope/deep geometry directly. 1 US gallon = 3.785411784 L; Imperial gallons are not used.
