Pool Size Chart: Dimensions & Gallons
A quick-reference pool size chart with water volume in US gallons for common inground rectangular pools and round above-ground pools, plus the formulas to size your own.
Quick answer: A 16 by 32 foot inground pool at a 5-foot average depth holds about 19,200 US gallons. A 12 by 24 holds about 10,800 gallons and a 20 by 40 holds about 29,900 gallons. A 24-foot round above-ground pool at a 4-foot water depth holds roughly 13,600 gallons. Rectangular gallons = length x width x average depth x 7.48. Round gallons = diameter x diameter x average depth x 5.9.
Knowing how many gallons your pool holds is the single most useful number in pool care. Every chemical dose is calculated per a set volume of water, so an accurate gallon figure keeps your chlorine, pH, and alkalinity on target. The chart below covers the most common pool sizes. If yours is not listed, use the pool volume calculator for an exact figure in seconds.
Inground rectangular pool sizes (5-foot average depth)
These are nominal dimensions for a standard inground pool with a shallow end and a deep end averaging 5 feet. Gallons are rounded to the nearest hundred.
| Pool size (ft) | Surface area (sq ft) | Average depth (ft) | Volume (US gallons) |
|---|---|---|---|
| 12 x 24 | 288 | 5 | 10,800 |
| 14 x 28 | 392 | 5 | 14,700 |
| 16 x 32 | 512 | 5 | 19,200 |
| 18 x 36 | 648 | 5 | 24,200 |
| 20 x 40 | 800 | 5 | 29,900 |
If your pool is shallower or deeper than 5 feet, the volume scales directly with depth. A 16 by 32 pool at a 4-foot average holds about 15,300 gallons, and at a 5.5-foot average it holds about 21,100 gallons. See the full grid on our pool volume chart.
Round above-ground pool sizes (4-foot water depth)
Above-ground pools are sold by wall height (commonly 52 inches) but filled only to the skimmer, so the working water depth is closer to 4 feet. These figures assume a full 4-foot depth.
| Diameter (ft) | Wall height | Water depth (ft) | Volume (US gallons) |
|---|---|---|---|
| 15 ft round | 52 in | 4 | 5,300 |
| 18 ft round | 52 in | 4 | 7,600 |
| 24 ft round | 52 in | 4 | 13,600 |
| 27 ft round | 52 in | 4 | 17,200 |
A 48-inch wall pool filled to the skimmer averages about 3.5 feet of water, which lowers each figure by roughly 12 percent. For example, a 24-foot round at a 3.5-foot depth holds about 11,900 gallons instead of 13,600.
How to read and use this chart
Find your pool size in the left column and read across to the gallons. That single number drives every other calculation in pool care: chlorine dosing, shock amounts, stabilizer additions, acid demand, and salt for a saltwater pool. Write it on a label at the equipment pad so you never have to recalculate.
The formulas behind the numbers
For a rectangular or square pool, the volume is length times width times average depth times 7.48 gallons per cubic foot. The 7.48 figure is the number of US gallons in one cubic foot of water and never changes.
For a round pool, the volume is diameter times diameter times average depth times 5.9. The 5.9 multiplier already folds in both the circle area constant and the 7.48 conversion, so you do not need a separate step. An oval pool uses long diameter times short diameter times average depth times 5.9.
For freeform, kidney, or lagoon shapes, estimate an average length and average width, treat it as a rectangle, then multiply by about 0.85 to trim the curved corners. This gets you within a few percent, which is plenty accurate for dosing.
Average depth, not maximum depth
The most common volume mistake is using the deep-end depth for the whole pool. Always use average depth: the shallow end plus the deep end, divided by two. A pool that runs 3 feet to 8 feet averages 5.5 feet, not 8.
Why the right gallon count matters
Pool chemicals are dosed per a fixed number of gallons. Underestimate your volume and you will chronically under-chlorinate, inviting algae and cloudy water. Overestimate it and you waste product and push pH and other levels around more than you need to. Get the gallons right once and the rest of pool care becomes simple bookkeeping.
Ready to nail down your exact number? Run your measurements through the pool volume calculator, then use it to size every chemical dose with the chlorine calculator and the rest of our tools.
Frequently Asked Questions
How do I calculate the gallons in my own pool?
For a rectangular pool, multiply length times width times average depth in feet, then multiply by 7.48 (gallons per cubic foot). For a round pool, multiply diameter times diameter times average depth times 5.9. Average depth is the shallow end depth plus the deep end depth, divided by two. Our pool volume calculator does the math for you and handles oval and kidney shapes.
Why does my above-ground round pool hold less than the chart shows?
Above-ground pools are rated by wall height (48 or 52 inches) but they are never filled to the very top. You fill to the skimmer, roughly 6 inches below the rim, so actual water depth is closer to 3.5 to 4 feet. The chart figures here use a 4-foot average water depth, which is realistic for most 52-inch walls filled to the skimmer.
What is the average depth if my pool has a deep end?
Add the shallow end depth and the deep end depth, then divide by two. A pool that is 3 feet in the shallow end and 7 feet in the deep end has an average depth of 5 feet. The chart on this page uses a 5-foot average for inground rectangular pools, which fits most family pools with a gentle slope.
How accurate do my pool gallons need to be?
Close is fine for routine chemical dosing. Being off by a few hundred gallons will not hurt anything because you always retest and adjust. Just avoid large errors: dosing a 30,000-gallon pool as if it were 15,000 gallons would double your chemicals. Measure your real dimensions once, write the gallons on the equipment pad, and reuse that number.
Does pool shape change the volume a lot?
Yes. A round or oval pool holds less water than a rectangle of the same length and width because the corners are cut off. For freeform or kidney-shaped pools, estimate the average length and average width, calculate as a rectangle, then multiply by about 0.85 to account for the curves. Our calculator includes shape factors so you do not have to guess.
Why is knowing my gallons so important?
Every chemical dose, from chlorine to acid to stabilizer, is figured per a set number of gallons. The right volume keeps your free chlorine, pH, and alkalinity on target and prevents both under-treating (cloudy or unsafe water) and over-treating (wasted product and harsh water). One accurate gallon figure is the foundation of every other pool calculation.
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