🏊 Pool Volume Calculator
Enter your pool's shape and dimensions to find how many gallons it holds, in US gallons, UK gallons, cubic feet, and litres. It's the foundation number for dosing chemicals and sizing your pump and heater.
💧 Shape & Size In, Gallons Out
Pool safety comes first
- Fence the pool on all four sides, at least 4 feet high and not climbable, with a self-closing, self-latching gate (Pool Safely, CPSC). A fence all the way round is better than using the house as the fourth side.
- Always watch children in or near the water and never leave them unattended; name one adult as the Water Watcher (Pool Safely).
- Drain covers should meet the federal safety standard behind the Virginia Graeme Baker Pool & Spa Safety Act (public pools and spas must have them); powerful drain suction can trap a swimmer underwater. Replace a broken or missing cover before anyone swims.
- Pumps, heaters and other pool equipment need GFCI protection, and an electrician qualified in pool and spa work should install and inspect them (CPSC).
What is a Pool Volume Calculator?
It converts the physical size of your pool into the volume of water it holds. Choose round, rectangular, or oval, give the key dimensions in feet and the depths at each end, and it applies the right area formula, multiplies by the average depth, and returns the total in three units at once.
Knowing your gallons is the starting point for balanced water: chlorine, salt, alkalinity, and heater calculations all scale directly with volume. Measure it accurately once and every other pool calculation gets easier — but remember these are estimates, so re-test your water after any addition.
❓ Frequently Asked Questions
Why do I need to know my pool's volume?
Almost every pool decision depends on it: how much chlorine or salt to add, what size pump and heater you need, and how long the filter must run. A wrong gallon count throws every dose off, so it is worth measuring once and writing it down.
How do I measure the average depth?
For a pool that slopes evenly from a shallow end to a deep end, the average depth is simply (shallow depth + deep depth) ÷ 2 — which is exactly what this calculator uses. For a flat-bottomed above-ground pool, enter the same value for both ends. If your floor has a sudden drop or a hopper, the true average will differ, so treat the result as an estimate.
Do I measure in feet or metres?
Enter all dimensions in feet. The tool multiplies them to cubic feet, then converts to US gallons (× 7.48052), UK gallons (4.54609 litres each, 20% larger than a US gallon) and litres, each rounded down. Use the unit your product label uses. If you have metric measurements, convert them to feet first (1 metre ≈ 3.281 feet) before entering.
My pool is a freeform or kidney shape — what do I do?
Pick the shape closest to yours — oval usually approximates a rounded freeform pool best, and rectangular works for L-shapes if you calculate each rectangle and add them. The result is an estimate. For chemical dosing never round the volume up: use the lower figure, follow the product label, and re-test the water after adding anything.