How do I calculate my pool volume in gallons?

Multiply your pool's surface area by the average depth, then multiply by 7.481 (the number of gallons in a cubic foot). For example, a 30 ft × 15 ft rectangular pool with an average depth of 5.5 ft holds about 30 × 15 × 5.5 × 7.481 = 18,514 gallons.

What is the formula for a round pool volume?

For a round pool: Volume = π × (diameter ÷ 2)² × average depth × 7.481. For example, an 18 ft diameter pool with a uniform 4 ft depth holds about 3.14159 × 9² × 4 × 7.481 = 7,614 gallons.

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

Measure the length and both widths (narrow end and wide end). The formula is: Volume = (Width A + Width B) ÷ 2 × Length × Average Depth × 7.481 × 0.45. The 0.45 factor accounts for the kidney curve.

How many gallons is a typical 12×24 rectangular pool?

A 12 × 24 ft rectangular pool with a 3 ft shallow end and 8 ft deep end (5.5 ft average) holds approximately 12 × 24 × 5.5 × 7.481 = 11,849 gallons.

How do I convert pool volume from gallons to liters?

Multiply US gallons by 3.785 to get liters. For example, 15,000 gallons × 3.785 = 56,781 liters. This calculator shows both units automatically.

Why is knowing my pool volume important?

Pool volume is essential for accurate chemical dosing (chlorine, pH, algaecide), sizing pumps and filters, estimating heating costs, planning water changes, and purchasing the right solar cover.

How do I calculate pool volume with a sloped bottom?

Measure the shallow end depth and deep end depth separately. The calculator uses the average: (shallow + deep) ÷ 2. For a pool that's 3 ft at the shallow end and 8 ft at the deep end, the average depth is 5.5 ft.

What's the difference between above-ground and in-ground pool volume calculation?

The volume formula is the same. The only difference is that above-ground pools typically have uniform depth (no slope), while in-ground pools usually have a shallow and deep end requiring an average depth calculation.

Pool Volume Calculator

Pool Shape

Formula:V = L × W × avgD × 7.481

Dimensionsin ft

Length

Width

Depth

Shallow End

Deep End

Average depth: 5.5 ft

Pool Volume

18,514US gallons

Rectangular pool · Avg depth 5.5 ft

Volume in All Units

Pool water volume converted to common units

US Gallons

18,514gal

Liters

70,084L

Cubic Feet

2,475.0ft³

Cubic Meters

70.08m³

UK Gallons

15,416imp gal

Water Weight & Fill Time

Weight of water and estimated fill time with a garden hose

Water Weight

154,409lbs

Water Weight

70,039kg

Fill Time (garden hose)

34.3hours

Pool Surface Area

Useful for solar cover sizing and chemical dosing

Surface Area

450ft²

Surface Area

41.8m²

What Is a Pool Volume Calculator?

Overview of the tool and why accurate pool volume matters.

A pool volume calculator estimates the amount of water your swimming pool holds. Knowing your pool's volume in gallons or liters is essential for accurate chemical dosing, equipment sizing, heating cost estimation, and water change planning. This calculator supports 7 pool shapes and outputs volume in US gallons, liters, cubic feet, cubic meters, and UK gallons simultaneously.

pool shapes

Most in class

7.481

gal / ft³

Conversion factor

output units

Gal, L, ft³, m³, UK gal

Pool Volume Formulas by Shape

Core formulas used for each pool type. All assume average depth = (shallow + deep) / 2.

Rectangular Pool

Volume (gal) = Length × Width × Avg Depth × 7.481

Round / Circular Pool

Volume (gal) = π × (Diameter/2)² × Avg Depth × 7.481

Oval Pool

Volume (gal) = π × (L/2) × (W/2) × Avg Depth × 7.481

Kidney-Shaped Pool

Volume (gal) = (WidthA + WidthB)/2 × Length × Avg Depth × 7.48 × 0.45

L-Shaped Pool

Volume (gal) = (L₁×W₁ + L₂×W₂) × Avg Depth × 7.481

Freeform / Irregular

Volume (gal) = Surface Area × Avg Depth × 7.481

Grecian Pool

Volume (gal) = Length × Width × Avg Depth × 7.48 × 0.85

Conversions: 1 ft³ = 7.481 US gal. 1 US gal = 3.785 L. 1 US gal = 0.833 UK gal. Water weighs 8.34 lbs per US gallon.

Common Pool Sizes Reference

Quick-reference volumes for popular pool dimensions.

Pool Size	Avg Depth	US Gallons	Liters
12 × 24 ft	5.5 ft	11,849	44,854
16 × 32 ft	5.5 ft	21,065	79,740
18 × 36 ft	5.5 ft	26,661	100,921
20 × 40 ft	5.5 ft	32,914	124,594
15 ft round	4 ft	5,288	20,016
18 ft round	4 ft	7,614	28,823
24 ft round	4 ft	13,536	51,241

Why You Need to Know Your Pool Volume

Practical reasons why accurate volume is critical for pool owners.

Chemical dosing

Chlorine, pH adjusters, and algaecides are all dosed per gallon. Incorrect volume means over- or under-treating your water.

Pump & filter sizing

Equipment is rated for specific volume ranges. An undersized pump won't achieve proper turnover (all water filtered in 8–12 hours).

Heating costs

Volume directly determines energy costs for pool heaters and heat pumps — a 20% volume error means 20% budget error.

Fill & drain time

Planning water changes or initial fills requires volume to estimate time and water costs.

Solar cover sizing

Surface area (also calculated here) determines the right solar blanket size for heat retention.

Common Mistakes When Calculating Pool Volume

Avoid these errors that can throw your estimate off by 20% or more.

Mixing units

Entering feet for length but inches for depth gives wildly wrong results. Keep all measurements in the same unit system.

Measuring to wall top, not waterline

Pools typically have 6" of freeboard. Measure to the waterline for accurate volume.

Ignoring slopes

A pool with a 3 ft shallow end and 8 ft deep end has an average depth of 5.5 ft — not 8 ft.

Wrong shape selection

A kidney pool is not the same as an oval. Using the wrong shape factor can be off by 20% or more.

Forgetting shape corrections

Kidney (0.45) and Grecian (0.85) pools have correction factors because they aren't simple rectangles.

Frequently Asked Questions

Common questions and detailed answers

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Last updated Mar 25, 2026