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, at every diameter the round pool shelf comes in. Water goes up with the square of the diameter, so the jump from 24 to 27 feet costs more water than the jump from 8 to 15.
| 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 small enough that every rule of thumb written for a real pool is wrong here. It is about an eighth of what an 18 foot round holds, and the chemical dose is a measuring cup rather than a jug. Buying a one gallon jug of liquid chlorine to shock this pool would take it to well over a hundred parts per million, which is a pool nobody can swim in for days.
The fill time is the good news. Two hours on an ordinary garden hose at eight gallons a minute, which means you can set it up and swim the same afternoon. That is the whole appeal of the size, and it is worth checking your own hose rather than trusting the eight, because a long coiled hose on low pressure runs closer to four.
At 3.9 tons of water it still wants flat, compacted ground. The failure on a pool this size is almost never the pool, it is a slope that looked level by eye. Water finds the low side, the wall leans, and a leaning wall on a soft edge is how a small pool empties itself in one go.
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
Is that the number printed on the box?
It is the same basis. A manufacturer quotes the pool filled to the top of the wall, which is what this page computes. In the yard you fill to the middle of the skimmer mouth, roughly six inches down, so the water actually in it lands about ten percent under the printed figure. Both numbers are useful: buy the cover and the liner off the printed one, and dose chemicals off the real one.
Does an 8 ft pool need a pump at all?
It needs circulation, not horsepower. At 941 gallons a turnover in eight hours is about two gallons a minute, which the cartridge pump packed in the box already does several times over. The thing that actually keeps it clear is running it long enough each day, not running a bigger one.
Does the water weight matter?
It decides what the pool can stand on. A gallon of water weighs 8.34 pounds, so the load is real tonnage and it is spread over the footprint rather than carried on a beam. A round above ground pool wants level, compacted ground, not a deck and not a slope that has been shimmed flat on one side. The ground under it settles once, when you fill it.
The pool volume calculator takes any dimensions you like and hands back the same list.