Pool Volume Calculator
for Gallons & Litres

A pool volume calculator tells you exactly how much water your swimming pool holds — in US gallons and litres — from a few simple measurements. That single number is the foundation of every pool maintenance decision you will make: how much chlorine to add, how much muriatic acid to lower pH, how much salt your chlorinator needs, how long to run the pump, and what it costs to heat or refill the pool.

Most pool owners guess their capacity from a vague chart or, worse, dose chemicals by eye. Guessing leads to under-dosing (algae blooms, cloudy water) or over-dosing (bleached liners, wasted money, irritated eyes). Our free pool calculator removes the guesswork: choose your shape, enter the dimensions, and get an accurate swimming pool volume calculator result instantly — no signup, no account, no cost.

This page explains how to calculate pool volume yourself with the standard formulas, gives you a quick reference table of common pool sizes, and shows how to put your volume to work across our full suite of pool calculators.

Every pool volume calculation starts with surface area multiplied by average depth, then converted from cubic feet to gallons. One cubic foot of water holds 7.48052 US gallons (field formulas often round to 7.5). If your pool has a shallow end and a deep end, find the average depth first: (shallow depth + deep depth) ÷ 2. Always measure the actual water depth, not the wall height — pools are rarely filled to the rim.

US chemical labels dose by gallons; Australian and UK labels read litres (or mg/L, which is the same as ppm). Converting is simple: 1 US gallon = 3.78541 litres, and 1 cubic foot = 7.48052 gallons = 28.3168 litres. Multiply a gallons figure by 3.78541 to get litres, or divide litres by 3.78541 to get gallons.

Our pool volume calculator litres view and pool calculator gallons view show both units at once — switch between gallons and litres with one tap, so you can match whichever number appears on your chemical bottle without converting anything yourself.

Chemical dosing is a per-gallon calculation. Raise chlorine by 2 ppm in a 10,000-gallon pool and you need a very different amount than in a 25,000-gallon pool — the same logic applies to every product on the shelf. Once you know your volume, put it to work:

• Chlorine & shock: daily maintenance and shock doses scale directly with gallons — use the pool chlorine calculator.
• Muriatic acid: lowering pH and alkalinity is measured in fluid ounces per 10,000 gallons — our muriatic acid pool calculator (inside the chemical calculator) gives the exact dose for your volume.
• Salt: initial fill and conversion doses are pounds of salt per gallon — use the salt pool calculator.
• Heating & filling: BTU requirements, warm-up time and refill cost all start from your volume — see the heating and cost calculators.

The volume calculator passes your result straight into each of these tools, so you never have to re-enter or re-convert your numbers.

An Olympic-size swimming pool measures 50 metres long, 25 metres wide and at least 2 metres deep — a volume of 2,500 cubic metres: 2,500,000 litres, or about 660,000 US gallons. It takes roughly 44 typical backyard pools (about 15,000 gallons each) to fill one Olympic pool.

Why does this benchmark matter? It gives you a sanity check for your own numbers. If your calculator says your 16 × 32 ft backyard pool somehow holds "500,000 gallons," you've entered the wrong unit or an extra zero — a standard pool of that size holds closer to 19,000 gallons, about 1/35 of an Olympic pool. Use the reference table or the calculator above to confirm you're in range before dosing.