Work out how much water a pool holds, from its shape, size and depth, in litres, m³, US and UK gallons, with fill time.
The volume of a pool is its surface area multiplied by its average water depth. A rectangular pool 8 m long and 4 m wide, with a floor that slopes evenly from 1 m to 2 m deep, has an average depth of 1.5 m, so it holds 8 × 4 × 1.5 = 48 m³, which is 48,000 litres, 12,680 US gallons or 10,559 imperial gallons. In feet, the quick rule is length × width × average depth × 7.48 for US gallons, because 1 cubic foot is 28.316846592 litres, or 7.4805 US gallons. The formula box shows each step for your own numbers.
A round pool has an area of π × (diameter ÷ 2)². A pool 5 m across and 1.2 m deep holds π × 2.5² × 1.2 = 23.56 m³, or 23,562 litres. An oval pool is an ellipse with an area of π ÷ 4 × length × width, so 6 m by 3 m at 1.5 m deep is 21.2 m³. A kidney pool has no exact formula. The page uses the usual pool-trade approximation, 0.45 × (width of the wide lobe + width of the narrow lobe) × length × depth, so treat a kidney result as an estimate and check it against the pool builder's figure if you have one.
Many pools are shallow at one end and deep at the other. If the floor is an even slope, the average depth is the shallow depth plus the deep depth, divided by two, so 1 m and 2 m average 1.5 m. If the floor stays flat and then drops steeply, as in a pool with a shallow shelf and a deep end, the simple average overstates or understates the water, and the best method is to split the pool into sections and add their volumes. Measure the depth of the water, not the height of the wall, because the water line sits below the top of the pool.
Type the flow of your hose or pump and the page divides the volume by it: 48,000 litres at 40 litres per minute takes 1,200 minutes, or 20 hours. A garden hose often gives less than the pump rating, so measure it with a bucket and a watch. Chemical doses are quoted per volume on the product label, so use the litre or gallon figure that matches the label. The estimate ignores steps, benches, rounded corners and an irregular floor, and it does not include the water in a spa or a filter system.
With a constant 4 foot depth it is 16 × 32 × 4 = 2,048 cubic feet, which is 15,320 US gallons or 57,993 litres. If the pool slopes from 3 to 8 feet the average is 5.5 feet, which gives 21,065 US gallons.
Use π × (diameter ÷ 2)² × average depth. A 5 m wide, 1.2 m deep pool holds 23.56 m³ or 23,562 litres. In feet, a 15 foot pool 4 feet deep holds about 5,288 US gallons.
1 cubic metre is 1,000 litres, 264.17 US gallons or 219.97 imperial gallons. So 48 m³ is 48,000 litres and 12,680 US gallons.
Divide the volume by the flow. 48,000 litres at 40 litres per minute takes 20 hours. A 15,000 US gallon pool at 10 US gallons per minute takes 1,500 minutes, which is 25 hours.
It is an approximation using 0.45 × (A + B) × length × depth, where A and B are the two lobe widths. A kidney 8 m long, 4 m and 3 m wide lobes, 1.5 m deep gives 37.8 m³. The true figure depends on the exact curve.
No. The sizes stay in this tab and are not stored or sent. Reloading puts the 8 by 4 metre example back. The page only counts that a result was shown, with none of your numbers.