Pool Volume Calculator
Find how many gallons or liters your pool holds using its shape, dimensions, and average water depth. Compare rectangular, circular, oval, and kidney-shaped estimates in seconds.
Calculate your pool volume
Measure the water surface, not the deck. Use average water depth for sloping floors.
US gallons (approximate)
Results are geometric estimates, not measured pool capacity. Irregular walls, steps, benches and curved floors can change actual volume.
Quick answer: how many gallons are in my pool?
For a rectangular pool, multiply length × width × average water depth × 7.48052 when measurements are in feet. A 30 × 15-foot pool averaging 5 feet deep holds approximately 16,831 US gallons. The calculator above also handles round and oval pools and converts to liters automatically.
How to use the pool volume calculator
- Select the shape closest to your pool: rectangular, round, oval or kidney/freeform.
- Choose feet or meters, then enter the water-surface length and width (or diameter for round pools).
- Enter shallow and deep water depths. If the floor is level, enter the same depth twice.
- Read the estimated US gallons, liters, cubic feet, average depth and surface area.
- For irregular pools, calculate simpler sections separately and add their volumes instead of relying on one rough outline.
Pool volume formulas by shape
| Shape | Volume in cubic feet | Convert to US gallons |
|---|---|---|
| Rectangle / square | Length × width × average depth | × 7.48052 |
| Round | π × (diameter ÷ 2)² × average depth | × 7.48052 |
| Oval / ellipse | π ÷ 4 × length × width × average depth | × 7.48052 |
| Kidney / freeform | Approx. 0.75 × length × width × average depth | × 7.48052 |
The kidney factor is a rough planning approximation, not a universal geometric formula. Kidney and freeform pools vary widely; subdividing into measured sections or using builder specifications can be substantially more accurate.
Worked examples: gallons by pool size
| Pool measurements | Assumed average depth | Estimated gallons |
|---|---|---|
| 12 × 24 ft rectangle | 4 ft | 8,618 |
| 15 × 30 ft rectangle | 5 ft | 16,831 |
| 20 × 40 ft rectangle | 5 ft | 29,922 |
| 18 ft diameter round | 4 ft | 7,615 |
| 15 × 30 ft oval | 4 ft | 10,576 |
These are calculated examples, not measured pools. For water replacement planning, use the pool fill time calculator after estimating the volume you need to add.
How to estimate average depth correctly
For a simple, evenly sloped floor, the midpoint of shallow and deep water depths often provides a useful average. For example, 3 feet shallow and 7 feet deep gives an estimated average of 5 feet. But a pool with a large shallow shelf and a small deep hopper does not have a uniformly sloping floor. In that case, measure the lengths of each section and calculate separate volumes.
Measure from the water surface to the floor at each point. Exclude steps, benches and raised platforms when you need a more accurate dose calculation. Pool construction drawings or the builder's stated water capacity may be more reliable than a rough geometry estimate.
Why pool gallons matter
Water volume is a starting input for several other calculations. The pool turnover time calculator uses gallons and measured operating flow to estimate circulation time; the pool heating time calculator uses water volume and temperature rise to estimate heating duration.
When balancing water, use your best volume estimate with current test results and product labels. The pool chlorine calculator, pool alkalinity calculator and pool salt calculator address different water-care questions; no single volume estimate replaces testing.
Common mistakes that change your estimate
- Using outside dimensions: measure the inside water surface, not coping or deck edges.
- Using total wall height: water depth is usually lower than the top of the pool wall.
- Assuming every deep end is a uniform slope: hoppers and shelves need sectional estimates.
- Confusing US and imperial gallons: this tool reports US liquid gallons; 1 US gallon is approximately 3.78541 liters.
- Applying the oval formula to a stadium-shaped pool: an ellipse and a rectangle with semicircular ends are different shapes. Split the latter into a rectangle plus a circle.
- Overstating precision: rounding a geometric estimate to the nearest gallon does not make the pool's real capacity known to that accuracy.
Frequently asked questions
How many gallons is a 15 × 30 pool?
At an average water depth of 5 feet, a rectangular 15 × 30-foot pool holds about 16,831 US gallons. A different depth or shape changes the estimate.
How do I calculate a pool with a shallow and deep end?
For a simple uniform slope, average the two water depths. For a pool with a distinct shallow shelf, deep hopper or uneven floor, calculate separate sections and add the results.
How many liters are in one US gallon?
One US liquid gallon equals exactly 3.785411784 liters.
Is the volume of an oval pool the same as a rectangular pool?
No. An elliptical oval has about 78.5% of the area of its bounding rectangle. Some pools marketed as oval have straight sides and rounded ends, which require a different calculation.
Does the calculator include steps and tanning ledges?
No. The simple geometric model assumes a filled shape. Raised features displace water and reduce actual volume; subtract their approximate volume when necessary.
Can I use these gallons for chemical dosing?
Use them as a starting estimate, then follow product-label directions and verify the result with water testing. Uncertain pool geometry can cause a meaningful dose error.
What if my pool is an irregular shape?
Divide it into rectangles, circular segments or other measurable sections, estimate each section separately, then add them. If available, use the builder's water-capacity documentation.
Related calculators and guides
This tool estimates geometric water capacity. Results are not a substitute for builder specifications, measured water use or laboratory water tests.