Pool volume calculator: estimate gallons and liters.
Calculate rectangular, round, and oval pool volume from water dimensions in feet or meters. See the formulas, a worked example, and limits of the estimate.
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Calculate your pool volume
Measure the water, not the outside walls
Use rectangle for straight sides, circle for a round pool, and oval only for an ellipse. A pool with straight sides and semicircular ends is not an ellipse.
Use inside water dimensions. For a circle, enter its diameter, not radius. For an ellipse, use the full long and short axes.
Use actual water depth rather than wall height. Equal depths represent a flat floor; averaging the shallow and deep ends represents a uniformly sloping floor.
A long shallow platform plus a small deep diving well needs separate sections. Two end depths alone do not describe how much floor lies at each depth.
The formulas used here
Volume = length × width × average depth.
Volume = π × (diameter ÷ 2)² × average depth.
Volume = π × length × width ÷ 4 × average depth.
For a uniform slope: (shallow depth + deep depth) ÷ 2.
Cubic feet × 7.48051948 = US gallons. Cubic meters × 1,000 = liters. US gallons × 3.785411784 = liters.
Worked example: a 30 × 15 foot pool
For a rectangular pool that slopes uniformly from 3 to 7 feet, average depth is (3 + 7) ÷ 2 = 5 feet. Volume is 30 × 15 × 5 = 2,250 cubic feet. That is about 16,831 US gallons, or 63,713 liters.
Results of at least one gallon or liter are rounded to whole units for readability; smaller positive amounts display as less than one. That does not mean the pool measurement is accurate to one gallon. An error of 10% in average depth produces a 10% error in this volume estimate.
Steps, shelves, diving wells, and freeform pools
For a stepped floor, divide the pool into non-overlapping sections, calculate each using its own footprint and depth, and add the results. Exclude water displaced by solid steps and benches. For a strongly curved or irregular outline, obtain the builder’s documented operating volume or a more detailed survey.
A connected spa or balance tank complicates total system volume. Keep this calculator’s pool-basin estimate separate from the volume that a treatment label expects. Do not assume a photographed outline or an approximate oval is a precise measurement.
What this number can and cannot decide
Use the estimate to check a documented pool volume and to understand the scale of your pool. For chemical treatment, current measurements and the exact product label are still needed. This calculator does not select a chemical, calculate a dose, or tell you when swimming is safe.
Filter and pump selection also require flow limits and system resistance. Heater sizing requires temperature, weather, cover use, and equipment performance. The same pool volume can lead to very different equipment requirements.
Common questions
Are these US or Imperial gallons?
US liquid gallons. The calculator also displays liters; it does not display Imperial gallons.
Can I enter inches in the feet fields?
Convert inches to feet first by dividing by 12. For example, 42 inches is 3.5 feet. Do not enter 42 when the field asks for feet.
Why does my builder’s volume differ?
Check the operating waterline, steps, shelves, floor profile, and whether the builder included connected vessels. A simplified shape can overestimate usable water volume.
Sources and product instructions
The references below support the technical checks in this guide. Use the instructions for your exact product or local conditions when they differ from a general example.