Pick your pool’s shape, enter its size and depth, and see how much water it holds. If the floor slopes, enter the shallow and deep ends and the average depth is used. You need the volume to dose chemicals, size a pump or heater, and plan filling.
Same depth all over? Enter it in both boxes. Measure to the water line, not the top edge.
A typical garden hose delivers about 15–25 litres (4–6 US gallons) per minute. Time a bucket to measure yours.
Volume = surface area × average depth. For a sloping floor the average depth is (shallow + deep) ÷ 2, so a pool 1 m deep at one end and 2 m at the other averages 1.5 m.
Rectangle: length × width × average depth. An 8 m × 4 m pool averaging 1.5 m holds 48 m³, which is 48,000 litres (about 12,680 US gallons).
Round: π × (diameter ÷ 2)² × depth.
Oval: π × (length ÷ 2) × (width ÷ 2) × depth.
Kidney: (widest width + narrowest width) × length × 0.45 × depth, the standard pool-trade estimate.
1 cubic metre is 1,000 litres and weighs about a tonne; 1 cubic foot is 7.48 US gallons. Fill time is simply the volume divided by how many litres or gallons your hose delivers each minute.
Multiply length × width × average depth in metres to get cubic metres, then multiply by 1,000. An 8 × 4 m pool averaging 1.5 m deep holds 48 m³, or 48,000 litres.
Multiply length × width × average depth in feet, then multiply by 7.48 for US gallons. A 16 × 32 ft pool averaging 5 ft deep holds 2,560 ft³ × 7.48 ≈ 19,150 US gallons.
Measure the water depth at the shallow end and at the deep end, then average the two. For a pool with a steep hopper, the average is a slight overestimate.
Measure the full length, the width across the widest part, and the width across the narrowest part. Add the two widths, multiply by the length, then by 0.45 and the average depth.
Divide the volume by the hose’s flow rate. At 20 litres per minute, a 48,000-litre pool takes 2,400 minutes, which is 40 hours.
