Pool Volume Calculator (Rectangular L × W × D)
A rectangular pool’s water volume is length × width × average depth. Enter meters or feet; the result is cubic meters, liters, and US gallons (1 US gal = 3.785411784 L). Sloped floors should use the average depth. This is a geometry estimate, not a fill-valve calibration.
Volume75 m³
Liters75,000
US gallons19,813
Cubic feet2,648.6
How this calculation works
Metric: volume in m³ = L × W × D with all sides in meters. Liters = m³ × 1000. US gallons = liters ÷ 3.785411784.
Feet: the box is treated as feet, converted with 1 ft = 0.3048 m, then the same liter and gallon factors.
Use average depth if the floor slopes (shallow + deep) ÷ 2. Freeform and circular pools are not this formula.
Do not fill to the brim: tile lines and overflow sit below the coping. Chemical dosing uses this volume as a starting guess.
Worked example
10 m × 5 m × 1.5 m → 75 m³ = 75,000 L ≈ 19,813 US gallons. A 20×10×5 ft box is 1,000 ft³ ≈ 28,317 L.
Frequently asked questions
US or imperial gallons?
US gallons (3.785 L). The UK gallon is 4.546 L — this page does not use it.
What depth do I measure?
Water depth, not wall height. For a slope, average the shallow and deep ends.
Oval or round pool?
Not L×W×D. A circle uses πr² × depth; an oval needs a different plan-area formula.
Hot tub vs pool?
Same rectangle math if the tub is a box. Seats reduce volume — subtract a rough percent if you care about chemicals.
Liters vs tonnes of water?
Fresh water is about 1 kg per liter, so 75,000 L is about 75 tonnes. Salt water is denser.
Are inputs stored?
No. Browser only.
This tool is provided for general information only. Verify important figures independently. · Last reviewed: August 25, 2026