About this tool
The Pool Volume Calculator is a free, in-browser tool that works out how much water your swimming pool holds — the single number every chlorine, pH, alkalinity, and hardness dose depends on. Pick a shape (rectangle, round, oval, or kidney), enter the dimensions and the shallow and deep-end depths, and it returns the volume in US gallons, liters, and cubic units at once. Because most pools slope from shallow to deep, it uses the average depth (shallow + deep) / 2 so the estimate reflects the real water column.
The surface area is computed per shape: rectangle A = L × W, round A = π(d/2)², oval A = π(L/2)(W/2), and kidney A = 0.45 × (W1 + W2) × L. Volume in cubic feet is area × average depth, then US gallons = cubic feet × 7.48052 and liters = gallons × 3.78541. Choose metric and the same geometry is done in meters, giving cubic meters × 1000 = liters. Everything runs locally in your browser, so nothing you enter is uploaded.
As a worked example, a 20 ft × 10 ft rectangular pool that is 3 ft at the shallow end and 6 ft at the deep end has an average depth of 4.5 ft, a surface area of 200 ft², a volume of 900 ft³, and therefore about 6,732 US gallons (roughly 25,486 liters). Getting this figure right is essential — dosing chemicals against a wrong volume is the most common cause of over- or under-treating a pool.