Pool Volume Calculator — Gallons for Any Shape

Calculate your swimming pool's volume in gallons and liters for rectangular, round, or oval pools, including sloped-bottom depth averaging.

July 3, 2026

Pool Shape

Length (ft)

Width (ft)

Sloped bottom (different shallow/deep depths)

Shallow End Depth (ft)

Deep End Depth (ft)

Pool Volume (avg. depth 5.5 ft)

21,120 gallons

≈79,948 liters

Rectangular: L × W × Avg. Depth × 7.5. Round: π × Radius² × Avg. Depth × 7.5. Oval: L × W × 0.785 × Avg. Depth × 7.5. The 7.5 multiplier converts cubic feet to US gallons (1 ft³ ≈ 7.48 gallons). Use water depth, not wall height — pools are rarely filled to the very top. Irregular shapes can be estimated by breaking them into rectangles/circles and adding the results together.

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Reference Values

Last verified: Jul 2, 2026

Category	Range	What It Means	Status
Rectangular pool	Length × Width × Avg. Depth × 7.5	Multiply by 7.5 to convert cubic feet to US gallons.	Good
Round pool	π × Radius² × Avg. Depth × 7.5	Radius = diameter ÷ 2.	Good
Oval pool	Length × Width × 0.785 × Avg. Depth × 7.5	0.785 approximates π/4 for an oval footprint.	Good
Typical above-ground pool (15 ft round, 4 ft deep) ★	≈5,300 gallons	A common backyard size used as a sanity-check reference.	★ Best
Typical in-ground pool (16×32 ft, avg. 5 ft) ★	≈19,200 gallons	A common residential in-ground pool size.	★ Best

Source: Standard pool-volume geometry formulas (1 cubic foot ≈ 7.48 US gallons, rounded to 7.5 for estimating) as used by pool industry references and manufacturers.

Worked Examples

Rectangular Pool, Sloped Depth

Shape: Rectangular
Length: 32 ft
Width: 16 ft
Shallow Depth: 3 ft
Deep Depth: 8 ft

≈21,120 gallons

Average depth = (3+8)/2 = 5.5 ft. 32 × 16 × 5.5 × 7.5 = 21,120 gallons.

Round Above-Ground Pool

Shape: Round
Diameter: 15 ft
Depth: 4 ft

≈5,297 gallons

Radius = 7.5 ft. 3.14159 × 7.5² × 4 × 7.5 = 5,301 gallons.

Oval Pool

Shape: Oval
Length: 24 ft
Width: 12 ft
Depth: 5 ft

≈8,478 gallons

24 × 12 × 0.785 × 5 × 7.5 = 8,478 gallons.

How to Use This Calculator

1

Select your pool shape

Rectangular, round, or oval — each uses its own footprint-area formula.
2

Enter your dimensions

Length and width (or diameter for round pools), in feet.
3

Choose sloped or flat bottom

Sloped averages your shallow and deep end depths; flat uses a single depth.
4

Read your volume in gallons and liters

Use this figure for chemical dosing, filter sizing, or fill-time estimates.

What Each Value Means

Pool Volume (Gallons) (gallons): Total water capacity of the pool at the entered depth, in US gallons — the standard unit for pool chemical dosing instructions in the US.
Average Depth (feet): For sloped-bottom pools, the average of the shallow-end and deep-end depths, used instead of either extreme for an accurate total-volume estimate.

Frequently Asked Questions

Why multiply by 7.5 to get gallons?

One cubic foot of water holds about 7.48 US gallons. Pool calculators round this to 7.5 for simpler, faster estimating — the rounding introduces a negligible difference (about 0.3%) that doesn't matter for practical purposes like chemical dosing or fill-time estimates.

Should I measure wall height or water depth?

Always use water depth, not wall height. Pools are almost never filled all the way to the top of the wall — using wall height will overestimate your actual water volume, which throws off chemical dosing calculations that depend on an accurate gallon count.

How do I calculate an irregularly shaped pool?

Break the irregular shape into two or three simpler shapes — rectangles, circles, or triangles that approximate sections of the pool — calculate each section's volume separately using the appropriate formula, then add them together for a total estimate.

Why does my pool's average depth matter more than deep-end depth?

Chemical dosing, filter sizing, and heater sizing are all based on total water volume, not the deepest point. A pool with a 3 ft shallow end and 8 ft deep end has an average depth of 5.5 ft — using only the 8 ft deep-end measurement would significantly overestimate the actual volume and lead to over-dosing chemicals.

Is the volume the same whether I measure in feet or meters?

The formulas here use feet and output US gallons. If your measurements are in meters, convert to feet first (1 meter ≈ 3.281 ft) — or just use the liters figure this calculator also provides, which is calculated directly from the gallon result.