How Many Gallons in an 18x52 Pool?
Water in the pool
8,243 gallons
Round, 18 ft across, filled to a 52 in wall, which is 4.33 ft. The 52 in the name is the wall height in inches.
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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 diameter18 ft
- Width18 ft
- Shallow end depth4.33 ft
- Deep end depth4.33 ft
- Fill rate8 gal/min
- Turnover target8 hours
Water in the pool8,243 gallons
| Surface area | 254.5 sq ftpi r squared on the diameter |
|---|---|
| Average depth | 4.33 ftmidpoint of shallow and deep |
| Volume | 1,101.9 cu ft7.48 gallons in each |
| Water weight | 34.4 tons68,742 lb |
| Fill time | 17.2 hoursat 8 gallons a minute |
| Pump for turnover | 17.2 gal/minwhole volume once in 8 hours |
| Heater to raise 10 degrees | 687,000 BTU8.34 BTU per gallon per degree |
| Liquid chlorine for a 10 ppm shock | 0.66 gal12.5 percent, sold in gallon jugs, so buy 1 |
| Salt to reach 3,200 ppm | 221 lb6 bags at 40 lb, from zero |
The material list this produces
| Water, gallons | 8,243 |
|---|---|
| Liquid chlorine 12.5 percent, gal | 1 |
| Salt, 40 lb bags | 6 |
| Pump, gal/min | 18 |
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 | 1,629 gallons | 50.3 sq ft | 3.4 hours |
| 12 ft | 3,664 gallons | 113.1 sq ft | 7.6 hours |
| 15 ft | 5,724 gallons | 176.7 sq ft | 11.9 hours |
| 18 ft | 8,243 gallons | 254.5 sq ft | 17.2 hours |
| 21 ft | 11,219 gallons | 346.4 sq ft | 23.4 hours |
| 24 ft | 14,654 gallons | 452.4 sq ft | 30.5 hours |
| 27 ft | 18,546 gallons | 572.6 sq ft | 38.6 hours |
| 30 ft | 22,896 gallons | 706.9 sq ft | 47.7 hours |
| 33 ft | 27,704 gallons | 855.3 sq ft | 57.7 hours |
What else matters here
8,243 gallons. Same eighteen foot footprint as an 18x48 and 628 gallons more water, because the only thing that changed is four inches of wall. That is an eight percent bigger pool for no extra yard, which is the whole argument for the taller wall and it is a good one.
The four inches buy more than volume. A 52 inch wall lets the water sit high enough that an average adult is in it to the chest rather than the waist, and it gives the skimmer mouth somewhere to live without the surface dropping below it every time three people get in. Freeboard is the quiet reason taller walls are worth the money.
Seventeen hours on a hose and 34 tons standing on 255 square feet. Both of those say the same thing: the pad matters more than the pool. Dig to level, compact it, and check it with a long board and a real level rather than by eye, because at this size a one inch tilt puts an extra inch of water against the low wall all season.
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 a 52 inch wall worth it over a 48?
On the same diameter it is 628 more gallons here, about eight percent, and the water sits four inches higher for the same ground prep and the same footprint. The costs are a slightly dearer liner, slightly more chemical every time you dose, and a fill that runs about an hour longer. Most people who have owned both say the freeboard alone settles it.
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 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.