How many gallons is a 16x32 pool?

It depends on depth. A 16x32 pool with a flat 4-foot floor holds 16 × 32 × 4 × 7.48 = 15,319 gallons. With a sloped floor averaging 5.5 feet (say 3 ft shallow, 8 ft deep end) it holds 21,064 gallons. Depth moves the answer more than footprint does.

Why 7.48 gallons per cubic foot?

One US gallon is defined as 231 cubic inches, and one cubic foot is 1,728 cubic inches. 1,728 ÷ 231 = 7.48. Some pool charts round this to 7.5 for mental math; the difference is under 0.3%, but every number on this page uses the exact 7.48.

How do I calculate the volume of a kidney-shaped or freeform pool?

Irregular shapes have no clean formula, so measure the surface area instead: sketch the pool to scale on graph paper, count the squares (each square a known square footage), then switch this calculator to surface-area mode and enter the area with your average depth. That measurement beats any shape multiplier a chart can offer.

How do I find average depth on a pool with a slope?

Measure the shallow end and the deep end and average them: (shallow + deep) ÷ 2. The pool-sloped mode does this for you. The average assumes the slope is roughly even between the two depths, which is how pool charts have always done it; if your pool has a hopper or a flat shallow shelf, estimate the shelf and the bowl separately and add them.

Pool Volume Calculator (Rectangular, Round & Oval)

Enter your pool's shape and dimensions; get its volume in gallons, liters, cubic feet and the weight of the water.

Formula and example

Formula. Gallons = surface area (sq ft) × average depth (ft) × 7.48; the area is L × W for a rectangle, π × radius² for a round pool, and π × (L ÷ 2) × (W ÷ 2) for an oval.

Example. A 32 × 16 ft rectangular pool with a 3 ft shallow end and 8 ft deep end averages 5.5 ft: 32 × 16 × 5.5 × 7.48 = 21,064 gallons.

Pool shape

Length (ft)

Longest straight dimension of the pool.

Width (ft)

Widest straight dimension.

Flat floor (one depth) Sloped (shallow + deep)

Depth (ft)

Use the average if the floor slopes.

1 cubic foot of water = 7.48 US gallons exactly (1,728 ÷ 231 cubic inches); water weighs 8.345 lb per gallon. Both constants are fixed physics, not presets.

How to calculate pool volume

Every pool volume is the same three-step problem: find the surface area, multiply by average depth to get cubic feet, then multiply by 7.48 — the number of US gallons in a cubic foot (1,728 cubic inches ÷ 231, the gallon's legal definition). A rectangle's area is length × width. A round pool's area is π × radius² — an 18 ft diameter above-ground pool has a 9 ft radius, so 3.1416 × 81 = 254.5 sq ft. An oval treated as a true ellipse is π × half the length × half the width: a 30 × 15 ft oval covers 3.1416 × 15 × 7.5 = 353.4 sq ft. Irregular pools have no clean formula — measure the surface area (graph paper to scale, count squares) and enter it in surface-area mode; a measured area beats any shape multiplier.

Average depth is where most estimates go wrong. A flat-floored pool uses its one depth. A sloped pool uses (shallow + deep) ÷ 2 — the 3 ft + 8 ft example averages to 5.5 ft, and that single number moves the answer more than the footprint does: the same 32 × 16 pool holds 15,319 gallons at a flat 4 ft but 21,064 gallons at a 5.5 ft average. The two-end average assumes the slope runs roughly evenly between the ends; pools with a flat shallow shelf plus a steeply dropping bowl or a hopper bottom should be split into sections, each averaged on its own, then added.

The number matters because pool chemistry is dosed per gallon. Salt, chlorine, stabilizer and every other chemical addition starts from "how many gallons is this pool" — get it wrong and every dose after it is wrong in the same proportion. The weight line matters for construction questions: 21,064 gallons of water weighs about 175,776 lb (8.345 lb per gallon), which is why pool builders pour a serious slab. When you have your volume, the salt dosing and bleach dosing calculators take it from there.

Sources & review date

Shape formulas and the 7.48 gal/cu ft constant verified against The Pool Nerd's pool volume reference, fetched and checked October 2026.
Water weight 8.345 lb/gallon is the same constant our salt dosing math rests on; dosing practice follows TroubleFreePool's Pool Math, the community dosing calculator since 2007.
Worked examples on this page are computed by the page's own tested math, not copied from any chart.

Last reviewed: October 2026. Spotted a stale number? info@orbitalfour.com. Dimensions and depth are your inputs; the two constants (7.48, 8.345) are definitions, not presets.

Pool volume FAQs

How many gallons in an 18 ft round pool?

π × 9² × depth × 7.48. At a flat 4 ft floor that is 254.5 × 4 × 7.48 = 7,614 gallons; at 52 in (4.33 ft) of wall height, 8,248 gallons. Round above-ground pools are the easiest case — the wall height is the depth.

Is my oval pool really an ellipse?

Most "oval" above-ground pools are rectangles with rounded ends, closer to a rectangle's area than a true ellipse's (an ellipse covers about 78.5% of its bounding rectangle). If your pool looks rectangular with rounded corners, run it both ways and treat the difference — roughly 20% — as your uncertainty band, or measure the surface area and use surface-area mode.

Does a 0.3% difference between 7.48 and 7.5 matter?

For chemical dosing, almost never — test kits and dosing guidance carry more slop than that. For water delivery or construction loads, use the exact 7.48: on a 20,000 gallon pool the two constants differ by about 54 gallons, or 450 lb of water.

How accurate does my measurement need to be?

Multiply your percentage errors: a length 2% over and a depth 5% under leaves the volume about 3% low. A foot of depth on a 16 × 32 pool is 3,830 gallons, so depth is the measurement worth taking care over.