How do you calculate pool volume?
Volume is surface area × average depth. For a rectangular pool it's length × width × average depth; for a round pool, π × radius² × depth; for an oval, length × width × 0.785 × depth. Then convert cubic metres or cubic feet to litres or gallons (1 m³ = 1,000 L; 1 ft³ ≈ 7.48 US gallons). The calculator holds the formula for each shape and does the unit conversion, so you just measure and read off the answer.
What's the average depth if the pool slopes?
Most pools have a shallow and a deep end, so you use the average depth = (shallow + deep) ÷ 2, not one or the other. A pool 1 m at the shallow end and 2 m at the deep end averages 1.5 m. Getting this right matters because using only the deep-end depth can overstate the volume by a third or more — and then you'd overdose chemicals. The calculator asks for both depths and averages them for you.
Why you need the exact volume
Almost everything about running a pool is dosed per unit of water: chlorine, pH adjuster, algaecide, salt for a saltwater system — all specified as an amount per so many litres or gallons. Guess the volume and you either waste chemicals or fail to sanitise. The volume also sizes the heater and pump and sets your turnover time (how long to filter all the water). It's the one number every other pool decision leans on.
Litres, gallons and the US/UK difference
Pool volumes are quoted in litres in most of the world and US gallons in North America — and a US gallon (3.785 L) is not a UK/imperial gallon (4.546 L), a gap big enough to matter when dosing. A 50,000-litre pool is about 13,200 US gallons or 11,000 imperial gallons. The calculator shows litres and US gallons side by side so a product label from either market lines up with your pool.
Uses average depth and standard shape formulas. For an irregular or freeform pool, split it into sections and add the volumes.
Frequently asked questions
How do I calculate my pool's volume?
Multiply surface area by average depth: length × width × avg depth for a rectangle. Convert to gallons or litres (1 m³ = 1,000 L). The calculator does it for each shape.
How many gallons is my pool?
It depends on size and shape — a typical 8 × 4 m pool at 1.5 m average is about 48,000 L (~12,700 US gallons). Enter your dimensions above for the exact figure.
What average depth should I use?
The average of the shallow and deep ends: (shallow + deep) ÷ 2. Using only the deep end overstates the volume and leads to over-dosing chemicals.
How do I convert cubic metres to litres or gallons?
1 cubic metre = 1,000 litres = about 264 US gallons. 1 cubic foot ≈ 7.48 US gallons. The calculator converts automatically.
Why does pool volume matter for chemicals?
Chlorine, pH balancers and salt are all dosed per volume of water. An accurate volume means correct dosing — too little won't sanitise, too much wastes product and can irritate.