A 16 × 32 ft in-ground pool from 3½ ft at the shallow end to 8 ft at the deep end holds 22,023 gallons: 16 × 32 × 5.75 ft average depth × 7.48. A garden hose at 10 gpm fills it in about 37 hours, heating it by 10 °F takes 539 kWh before losses, and raising the chlorine by 3 ppm takes just under half a gallon of 12.5 % liquid chlorine. The calculator above works this out for rectangular, round and oval pools.
How the calculator works
Choose the shape and enter the size and the water depth at the shallow and deep ends (the same number for a flat floor). Then set the fill flow, the temperature rise, the chlorine product and the dose. The result is the volume in gallons and liters, the water surface, the wall and floor area for a liner or plaster, the time to fill, the heating energy and the chemicals.
Volume
| Pool | Formula | Example |
|---|---|---|
| Rectangular | L × W × average depth × 7.48 | 16 × 32 ft, 3½–8 ft: 22,023 gal |
| Round | π r² × depth × 7.48 | 24 ft, 4 ft deep: 13,536 gal |
| Oval | π × ½L × ½W × depth × 7.48 | 15 × 30 ft, 4 ft: 10,575 gal |
Heating
Water takes 1 Btu per pound per °F: 22,023 gallons × 8.34 lb × 10 °F = 1.84 million Btu, or 539 kWh. Surface losses at night and wind add to that every day; a cover cuts them most.
Chlorine
One part per million is one gram of available chlorine per cubic meter of water. The product needed is the dose divided by its strength: liquid chlorine is about 12.5 %, cal-hypo 65 %, trichlor 90 %. Keep free chlorine at 1–3 ppm and test before adding more.
Common mistakes
- Using the deep end depth. Average the two ends.
- Measuring to the coping. Use the water depth, usually 6 in below the top.
- Shocking by guesswork. Dose from the volume and a test kit.
For other tanks, use the Tank Volume Calculator.