How Many Gallons in a 15 Ft Round Pool?
Water in the pool
5,288 gallons
Round, 15 ft across, filled to a 48 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 diameter15 ft
- Width15 ft
- Shallow end depth4 ft
- Deep end depth4 ft
- Fill rate8 gal/min
- Turnover target8 hours
Water in the pool5,288 gallons
| Surface area | 176.7 sq ftpi r squared on the diameter |
|---|---|
| Average depth | 4 ftmidpoint of shallow and deep |
| Volume | 706.9 cu ft7.48 gallons in each |
| Water weight | 22 tons44,100 lb |
| Fill time | 11 hoursat 8 gallons a minute |
| Pump for turnover | 11 gal/minwhole volume once in 8 hours |
| Heater to raise 10 degrees | 441,000 BTU8.34 BTU per gallon per degree |
| Liquid chlorine for a 10 ppm shock | 0.42 gal12.5 percent, sold in gallon jugs, so buy 1 |
| Salt to reach 3,200 ppm | 142 lb4 bags at 40 lb, from zero |
The material list this produces
| Water, gallons | 5,288 |
|---|---|
| Liquid chlorine 12.5 percent, gal | 1 |
| Salt, 40 lb bags | 4 |
| Pump, gal/min | 12 |
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 | 1,505 gallons | 50.3 sq ft | 3.1 hours |
| 12 ft | 3,385 gallons | 113.1 sq ft | 7.1 hours |
| 15 ft | 5,288 gallons | 176.7 sq ft | 11 hours |
| 18 ft | 7,615 gallons | 254.5 sq ft | 15.9 hours |
| 21 ft | 10,364 gallons | 346.4 sq ft | 21.6 hours |
| 24 ft | 13,537 gallons | 452.4 sq ft | 28.2 hours |
| 27 ft | 17,133 gallons | 572.6 sq ft | 35.7 hours |
| 30 ft | 21,151 gallons | 706.9 sq ft | 44.1 hours |
| 33 ft | 25,593 gallons | 855.3 sq ft | 53.3 hours |
What else matters here
5,288 gallons is the first size where the pool starts behaving like a pool. The 48 inch wall is deep enough to stand in properly, the volume is big enough that a single dose mistake does not ruin the week, and it is still small enough to fill in one day. Eleven hours on a hose, so start it in the morning.
This is also the size where the pump in the box starts to matter. An eight hour turnover here is eleven gallons a minute, which is about 660 gallons an hour, and some of the starter cartridge systems shipped with 15 foot pools are rated under that. Nothing breaks if the pump is small, the water just goes cloudy in hot weather and stays cloudy.
22 tons of water on a 177 square foot footprint. That is around 250 pounds on every square foot, which is why the ground prep for a round pool is dig and compact, never build up. Filling low spots with loose soil and setting the wall on top of it is the single most common reason a first season above ground pool goes out of round.
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.
How long does it really take to fill?
Eleven hours at eight gallons a minute, which is a good outdoor spigot with a short hose. Measure your own first: run the hose into a five gallon bucket and time it. If the bucket takes 50 seconds you are at six gallons a minute and the fill is fourteen hours, not eleven. On a well, ask before you start, because a continuous draw that long can pull a shallow well down.
Why is the salt figure from zero?
Salt only leaves a pool with the water, through splash out, backwash and a leak. It does not evaporate. So the bag count here is what an empty pool needs to reach 3,200 ppm, and a pool that has run on salt before needs a test first or you will overshoot it. Adding salt is easy and taking it out means draining water.
The pool volume calculator takes any dimensions you like and hands back the same list.