How many gallons in a 21 ft round pool?
A 21 ft round above-ground pool holds about 10,400 gallons (39,200 liters) with 4 ft of water.
By water depth
| Water depth | US gallons | Liters |
|---|---|---|
| 3.5 ft (42 in) | 9,100 | 34,300 |
| 4 ft (48 in) | 10,400 | 39,200 |
| 4.5 ft (54 in) | 11,700 | 44,100 |
Formula: 3.14 × 10.5² × depth × 7.48. Measure the water, not the wall: water usually sits 4–6 inches below the top rail.
At 4 ft of water
Dose this pool: full chemical calculator · liquid chlorine · salt
Other round pool sizes
10 ft round · 12 ft round · 15 ft round · 18 ft round · 24 ft round · 27 ft round · 28 ft round · 30 ft round · 33 ft round
Questions pool owners ask
How many gallons are in a 21 ft round pool?
About 10,400 gallons at 4 ft (48 in) of water. At 3.5 ft it holds about 9,100 gallons and at 4.5 ft about 11,700. Formula: 3.14 × 10.5² × depth × 7.48.
How much salt does a 21 ft round pool need?
Starting from fresh water, about 277 lb of pool salt (7 × 40 lb bags) reaches 3,200 ppm at 4 ft of water. Add 80–90% first, then test after 24 hours.
How much liquid chlorine for a 21 ft round pool?
Raising free chlorine by 1 ppm takes about 13.3 fl oz of 10% liquid chlorine, or 21.5 fl oz of 6% bleach.
How long does it take to fill?
With a garden hose at about 10 gallons per minute, roughly 17 hours. Two hoses halve that.