Pool Volume Calculator
Find out how many gallons (or litres) of water your pool holds — rectangular, round or oval, flat or sloped floor — then scale any chemical's label dose to your pool. It measures the water; it doesn't tell you which chemical or target level to use.
Pool shape and size
Chemical dose from the product label (optional)
Before you dose
- Measure the depth of the water, not the height of the wall. Above-ground pools are never filled to the rim, and manufacturers usually quote capacity at about 90% full.
- There are two oval options, and they give different answers. "Oval with straight sides" has straight long sides and rounded ends, like most frame and above-ground ovals. "Oval (ellipse)" curves all the way round. At the same length and width, the ellipse holds about 10–15% less. Pick the one that matches your pool from above; the picture shows which shape is being calculated.
- Kidney, L-shaped or freeform pool? Split it into rectangles and circles, work each one out separately and add them up. If the floor has several different slopes, do the same for each section of constant slope.
- The dose scaler only rescales what the product label says. It doesn't know your product's strength or what level your water should be at. Add large doses in portions (for example a third at a time), let the water circulate and retest before adding more.
In the same unit as on the label (g, ml, oz…).
How this is calculated
The surface area of the water is worked out from the shape: length × width for a rectangle, π/4 × diameter² for a round pool, π/4 × length × width for an elliptical oval. An oval with straight sides is a rectangle plus two half-circles whose diameter is the pool's width. That area is multiplied by the average depth, which is the shallow-end and deep-end water depths added together and halved. This is the same method US public-health pool operator manuals teach. Cubic metres become litres (× 1000) and US gallons using the exact definition 1 US gallon = 3.785411784 L. Rules of thumb like "× 7.5", "× 5.9" or "× 0.89 for ovals" are rounded versions of the same geometry, so their answers differ from this one by a fraction of a percent. The 0.89 oval factor is only accurate for a pool twice as long as it is wide. The chemical dose is the label amount × (your pool volume ÷ the label's volume). When the label talks about a ppm or pH change, multiply also by (the change you need ÷ the label's change). That is the formula pool operators are taught.
Common questions
Why does another calculator give a different number for my oval pool?
Because "oval" covers two shapes. Some calculators treat it as a true ellipse (about 0.785 × length × width × depth). Others use a fixed factor of about 0.89 (or "× 6.7" in gallons), which matches an oval with straight sides and rounded ends that is twice as long as it is wide. The two answers are 12–14% apart. This calculator offers both shapes and works the straight-sided one out exactly, so it stays right for long, narrow ovals and short, wide ones too.
Does it tell me how much chlorine to add?
Only if you give it the dose from your product's label. Chlorine products range from about 10% (liquid) to 90% (trichlor) available chlorine, and the target level depends on your pool and local rules, so there's no safe one-size-fits-all number. Enter what the label says — for example "16 oz per 10,000 gallons", or "20 oz raises chlorine 10 ppm in 10,000 gallons" — and the calculator scales it to your pool. Always follow the manufacturer's instructions.
Are these US or UK gallons?
US gallons (3.785 litres). A UK (imperial) gallon is about 4.546 litres, so the same pool is about 17% fewer imperial gallons. Some UK retailers list pool capacity in imperial gallons. If in doubt, compare litres, which the calculator always shows too.
Part of Home Improvement Calculators