Pool volume calculator (gallons and liters)
For a rectangular pool, gallons = length × width × average depth × 7.48, with all sizes in feet.
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On this page (8 sections)
A 32 × 16 ft pool that runs from 3.5 ft to 8 ft deep holds about 22,023 gallons (83,365 liters), or about 19,868 gallons if the deep end is a short flat section after a steep drop.
Calculator: pick a shape, enter length, width, and depths
Choose the shape and enter sizes in feet or meters. You get US gallons, liters, and a link to the closest dose chart.
- Rectangle: length × width × average depth × 7.48.
- Round: diameter × diameter × average depth × 5.875 (that is π ÷ 4 × 7.48).
- Oval: two options. "Straight sides, round ends" matches most above-ground ovals. "True ellipse" is for pools that curve all the way around.
- Kidney: 0.45 × (narrow width + wide width) × length × average depth × 7.48. It is a common approximation, so treat the result as accurate to about ±10%, and calibrate if you can.
- L-shape: two rectangles added together.
Own an Intex or Bestway above-ground pool? Pick it under "Above-ground model": the calculator shows the capacity the maker lists and fills in the size. We list only models whose capacity we checked on the maker's product page. Not listed? Enter the size yourself.
For other above-ground pools, switch "Depth" to "Above-ground wall height". Water sits below the top rail, so the calculator uses your fill level (90% of the wall by default). It then corrects for leaning walls and rounded corners: × 0.93 for metal-frame and steel-wall pools, × 0.87 for inflatable-ring pools. Those factors come from our own comparison of 26 manufacturer capacities with their nominal geometry, so the result is labeled "about ±7%". If you know the model, its published capacity is better: see the above-ground pool gallons chart. Round and oval pools also have their own tools: the round pool calculator and the oval pool calculator.
Sloped floors and deep ends: average depth done right
Measure water depth, from the water surface to the floor, not from the deck. Then:
- Even slope from shallow to deep end: average depth = (shallow + deep) ÷ 2.
- Shallow area, steep drop, flat deep end (a "hopper" or "sport" layout): split the length into sections and weight each by its length.
The difference is bigger than most people expect. Take a 16 × 32 pool with 16 ft of floor at 3.5 ft, an 8 ft slope, and 8 ft of floor at 8 ft deep. The simple average is (3.5 + 8) ÷ 2 = 5.75 ft, which gives 22,023 gallons. The length-weighted average is 5.19 ft, which gives 19,868 gallons. The simple method overstates this pool by 11%.
L-shaped and freeform pools: split into sections
Break the outline into shapes that don't overlap, get the area of each, add them, and then multiply by the average depth and 7.48. An L-shaped pool made of a 30 × 15 ft section and a 10 × 8 ft section, 5 ft deep on average, holds about 19,823 gallons. A kidney pool 32 ft long, 10 ft wide at the narrow end and 14 ft at the wide end, 5 ft deep on average, holds about 12,926 gallons with the formula above. The kidney pool calculator uses the same math.
For freeform pools, draw the closest rectangles and half-circles you can, then check the result with one of the methods below.
Don't have a tape? Calibrate volume with a salt or hose test
Salt rise. This works best for salt water pools, which need salt anyway. Test salt, add a known weight of pool salt, run the pump, and wait 24 hours (the settling time Hayward gives for salt readings). Then test again and use this formula:
gallons = pounds of salt × 453.6 × 1,000 ÷ rise in ppm ÷ 3.785
Example: one 40 lb bag that raises the reading by 250 ppm means about 19,172 gallons. If the same bag raises it by 300 ppm, the pool holds about 15,977 gallons. The weak point is the test: a 10% error in the measured rise becomes a 10% error in volume. Use a digital salt reader or a titration kit rather than a strip, and add enough salt to get a clear rise.
Water meter or hose. If you are filling the pool anyway, read your water meter before and after. Many utility bills count water in CCF: 1 CCF is 100 cubic feet, about 748 gallons. No meter? Time your hose filling a 5-gallon bucket (30 seconds means 10 gallons a minute) and multiply by the total fill time in minutes. It is rough, since hose flow varies, but it catches big mistakes.
The Pooldex app will be able to recalibrate your saved volume from a salt top-up automatically, so you only measure once.
Common pool sizes and their gallons
Rectangular inground pools at three average depths (geometry only):
| Size (ft) | 4.5 ft average | 5 ft average | 5.5 ft average |
|---|---|---|---|
| 12 × 24 | 9,695 gal | 10,772 gal | 11,849 gal |
| 15 × 30 | 15,148 gal | 16,831 gal | 18,514 gal |
| 16 × 32 | 17,235 gal | 19,150 gal | 21,065 gal |
| 18 × 36 | 21,813 gal | 24,237 gal | 26,661 gal |
| 20 × 40 | 26,930 gal | 29,922 gal | 32,914 gal |
Round above-ground pools filled to 90% of the wall. "Estimate" applies our 0.93 frame-pool factor. Your model's published capacity is more accurate than both:
| Diameter | 48 in wall: geometry / estimate | 52 in wall: geometry / estimate |
|---|---|---|
| 12 ft | 3,046 / 2,832 gal | 3,300 / 3,069 gal |
| 15 ft | 4,759 / 4,426 gal | 5,155 / 4,795 gal |
| 18 ft | 6,853 / 6,373 gal | 7,424 / 6,904 gal |
| 24 ft | 12,183 / 11,330 gal | 13,198 / 12,274 gal |
Every size we cover, with real model capacities, is listed under pool sizes. Measuring a hot tub instead? Seats and jets make shape math unreliable. See how many gallons your hot tub holds.
Why a 10% volume error means a 10% dosing error
Every dose is ppm × volume, so any error in gallons passes straight into every chemical you add. For the 16 × 32 hopper pool above, using the simple-average 22,023 gallons instead of the real 19,868 means:
- 28 fl oz instead of 25 fl oz of 10% liquid chlorine per 1 ppm. A small waste, since extra chlorine is used up over time.
- 7.35 lb instead of 6.65 lb of stabilizer for a new fill, so CYA lands at about 44 ppm instead of 40. Stabilizer only leaves when you drain water.
- More acid than needed per step, which can push pH below 7.2.
Above-ground pools show the same effect from the other side. An Intex Easy Set 18 ft × 48 in pool works out to 6,091 gallons by geometry at an 80% fill, but Intex lists 5,455 gallons. Dosing by geometry would overdose it by about 12%. Once your volume is right, the pool chemical calculator uses it for every product.
FAQ
How do I calculate my pool volume?
Multiply surface area by average water depth, then convert cubic feet to gallons with 7.48. For a rectangle, the area is length × width. For a circle, it is diameter × diameter × 0.785. With a sloped floor, use (shallow + deep) ÷ 2, or a length-weighted average if the deep end is a separate flat section.
Sources
- Hayward, AquaRite manual (salt reading settling time): PDF
- Leslie's, How to calculate pool volume (kidney approximation): lesliespool.com
- Intex product pages (Easy Set 18 ft × 48 in, Prism Frame 15 ft × 48 in), read 2026-09-29: intexcorp.com
- Our volume formulas and the 26-model comparison: methodology