How Many Gallons in an 8 Ft Round Pool?
Water in the pool
941 gallons
Round, 8 ft across, filled to a 30 in wall. Flat bottom, so the average depth is the wall height.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Pool shapeRound
- Length or diameter8 ft
- Width8 ft
- Shallow end depth2.5 ft
- Deep end depth2.5 ft
- Fill rate8 gal/min
- Turnover target8 hours
Water in the pool941 gallons
| Surface area | 50.3 sq ftpi r squared on the diameter |
|---|---|
| Average depth | 2.5 ftmidpoint of shallow and deep |
| Volume | 125.7 cu ft7.48 gallons in each |
| Water weight | 3.9 tons7,840 lb |
| Fill time | 2 hoursat 8 gallons a minute |
| Pump for turnover | 2 gal/minwhole volume once in 8 hours |
| Heater to raise 10 degrees | 78,000 BTU8.34 BTU per gallon per degree |
| Liquid chlorine for a 10 ppm shock | 0.08 gal12.5 percent, sold in gallon jugs, so buy 1 |
| Salt to reach 3,200 ppm | 26 lb1 bags at 40 lb, from zero |
The material list this produces
| Water, gallons | 941 |
|---|---|
| Liquid chlorine 12.5 percent, gal | 1 |
| Salt, 40 lb bags | 1 |
| Pump, gal/min | 2 |
Diameter compared
Same wall height as this page, across round diameters from 8 to 33 feet. Water goes up with the square of the diameter, so doubling the diameter holds four times the water.
| Diameter | Water in the pool | Surface area | Fill time |
|---|---|---|---|
| 8 ft | 941 gallons | 50.3 sq ft | 2 hours |
| 12 ft | 2,116 gallons | 113.1 sq ft | 4.4 hours |
| 15 ft | 3,305 gallons | 176.7 sq ft | 6.9 hours |
| 18 ft | 4,759 gallons | 254.5 sq ft | 9.9 hours |
| 21 ft | 6,478 gallons | 346.4 sq ft | 13.5 hours |
| 24 ft | 8,461 gallons | 452.4 sq ft | 17.6 hours |
| 27 ft | 10,708 gallons | 572.6 sq ft | 22.3 hours |
| 30 ft | 13,220 gallons | 706.9 sq ft | 27.5 hours |
| 33 ft | 15,996 gallons | 855.3 sq ft | 33.3 hours |
What else matters here
941 gallons is about an eighth of the 7,615 in an 18 foot round with a 48 inch wall, and a 10 ppm shock is 0.08 of a gallon of 12.5 percent liquid chlorine.
The fill is two hours on a garden hose at eight gallons a minute. Time your own hose into a five gallon bucket rather than trusting the eight, because the fill time is the gallons divided by the flow.
The water weighs 3.9 tons, which is 7,840 pounds.
What this calculator assumes
- A cubic foot of water is 7.48 gallons and a gallon weighs 8.34 pounds. Those two numbers do all the work on this page.
- Average depth is taken as the midpoint of the shallow and deep ends. That is exact for a pool with one straight slope between them and slightly generous for a pool with a flat shallow shelf and a hopper, which is the safer way for it to be wrong when you are buying chemicals.
- A round pool uses the diameter and ignores the width. An oval is figured as an ellipse, which is length times width times pi over four, not as a rectangle.
- Turnover is the time the pump takes to move the whole volume once. Eight hours is the common residential target and some health codes for public water are stricter, so check yours before you size a commercial pump off this.
- Liquid chlorine trade percent is defined so that one gallon of it raises ten thousand gallons of water by that many parts per million. One gallon of 12.5 percent raises 10,000 gallons by 12.5 ppm, which is where the dose row comes from rather than a chart.
- Salt is figured from zero to 3,200 ppm, which is the middle of the range most chlorine generators want. A pool that already has salt in it needs a test first, because salt only leaves with the water.
Questions people ask
What pump flow does an 8 ft pool need?
About two gallons a minute. That turns the whole 941 gallons over once in eight hours, the common residential target.
How is the water weight worked out?
Gallons times 8.34 pounds, which is what a gallon of water weighs.
The pool volume calculator takes any dimensions you like and hands back the same list.