Find out how many gallons (or liters) your swimming pool holds — for any shape, with or without a sloped bottom. Free, instant, no email required.
Pool shape
Depth
Drag the orange handles to set where the slope starts and ends — or type the Shallow and Deep lengths above.
Measure the depth of your water, not the height of the wall. For pools with a slope, use Shallow + Deep so we average correctly.
Estimated volume
17,235gallons
≈ 65,242 liters
Servicing more than one pool? You don’t have to save — “Use in Chlorine Calculator” carries this volume over without storing anything.
L × W × Depth × 7.48 → 32 × 16 × [(9.6·3.5 + 12.8·((3.5+5.5)÷2) + 9.6·5.5) ÷ 32.0] = 4.5 ft avg
7.48 = U.S. gallons in 1 cubic foot of water.
Four quick tips for getting the right numbers into the fields above. The surface dimensions are easy — it’s depth that trips most people up, and depth is what moves your gallon count the most, so it’s worth measuring carefully rather than guessing.
Use a marked pole or weighted tape from the waterline straight down to the floor.
Enter both depths in the Depth section and we average them — or use Sloped sections for a section-accurate result.
Measure the widest points across the long axis and the short axis — that's what goes into Length and Width.
Mentally break it into rectangles and circles. Use Freeform mode and add each section separately — we sum them.
Why the fuss about depth? Because volume scales directly with it: in a 16-by-32-foot pool, every extra foot of average depth adds nearly 3,800 gallons. Get the length and width a few inches off and your total barely moves, but misjudge the average depth by a foot and you can be off by 15–20% — enough to throw every chemical dose that depends on this number. If your pool slopes, measure the shallow and deep ends and let the calculator average them; if it has distinct flat and sloped sections, the sloped-sections mode is more accurate still. When you genuinely can’t tell, round the depth down slightly so you don’t overstate your gallons.
Approximate gallons for standard residential pool dimensions.
| Shape | Dimensions | Gallons |
|---|---|---|
| Rectangle | 10 × 20 × 5 ft | 7,480 |
| Rectangle | 12 × 24 × 5 ft | 10,771 |
| Rectangle | 14 × 28 × 5 ft | 14,661 |
| Rectangle | 16 × 32 × 5 ft | 19,149 |
| Rectangle | 16 × 32 × 6 ft | 22,979 |
| Rectangle | 20 × 40 × 5 ft | 29,922 |
| Round | 15 ft Ø × 4 ft | 5,288 |
| Round | 18 ft Ø × 4 ft | 7,615 |
| Round | 24 ft Ø × 4 ft | 13,540 |
| Round | 27 ft Ø × 4 ft | 17,137 |
| Oval | 15 × 30 × 4 ft | 10,579 |
| Oval | 18 × 33 × 4 ft | 13,961 |
Quick answers to the questions homeowners ask about pool volume.
A 16-by-32-foot rectangular pool holds roughly 19,150 gallons at an average depth of 5 feet, or about 23,000 gallons at 6 feet of average depth. Depth makes the biggest difference: every extra foot of average depth adds about 16 × 32 × 7.48 = 3,830 gallons.
If your pool has a sloped bottom, add the shallow-end depth and the deep-end depth, then divide by two. That gives you the average for a uniform slope. For pools with a flat shallow section, a sloped middle, and a flat deep end, the sloped-sections mode in this calculator handles the geometry more precisely — measure each section length and the two depths.
Most in-ground residential pools in the US hold between 15,000 and 30,000 gallons. A common 16 × 32 with a 3-foot to 8-foot slope lands around 21,000 gallons. Above-ground pools are smaller: a 24-foot round above-ground pool at 4 feet deep is about 13,500 gallons.
Spas and hot tubs are much smaller — most residential spas hold 300 to 1,000 gallons. The math is the same (cylinder or rectangular box), but spas often have a seat or step bench that takes up water space. Use the 'Spa has a seat / step bench' option in this calculator to subtract that bench from the footwell volume automatically.
Multiply gallons by 3.785 to get liters. So a 20,000-gallon pool is about 75,700 liters. This calculator displays both — just toggle "Gallons" or "Liters" at the top.
Almost every pool-chemistry dose is “add X amount per 10,000 gallons,” so your volume is the multiplier behind every calculation. Guess too high and you under-dose and never reach your target; guess too low and you over-dose, waste chemicals, and can push levels into an unsafe range. Getting an accurate gallon figure once, here, makes every later result — chlorine, salt, alkalinity, acid, calcium — correct. That is why we recommend finding your volume first, then carrying that number into the dosing calculators.
For a standard rectangle, round, or oval with a uniform slope, a calculator is accurate to within a few percent — easily good enough for dosing. The main source of error is average depth, not the surface dimensions, so measure your shallow and deep ends carefully. Free-form and kidney-shaped pools are the hardest to estimate; for those, approximate the shape with the closest option and break unusual sections into pieces. When in doubt, round volume up slightly rather than down so you do not under-treat the water.
For a round pool, gallons = diameter × diameter × average depth × 5.9 (with all measurements in feet). A 24-foot round pool at 4 feet deep holds about 13,500 gallons; a 27-foot round at 4.5 feet is roughly 19,300 gallons; a smaller 15-foot round at 3.5 feet is around 4,650 gallons. Select the round shape above and enter your diameter and wall height to get the exact figure for your pool.
Pool pros: add this calculator to your own website as a free tool for your customers. Paste the code where you want it to appear — it auto-resizes to fit, on any device.
<iframe src="https://freepooltools.com/embed/pool-volume-calculator" title="Pool Volume Calculator" loading="lazy" width="100%" height="640" style="border:0;width:100%;max-width:680px" scrolling="no"></iframe>
<script>window.addEventListener("message",function(e){if(e.data&&e.data.type==="fpt-embed-height"){var f=document.querySelectorAll('iframe[src*="/embed/"]');for(var n=0;n<f.length;n++)if(f[n].contentWindow===e.source)f[n].style.height=e.data.height+"px"}});</script>How much liquid chlorine, bleach, or shock to add to hit your target free chlorine.
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