Pool Volume Calculator — free PoolPad tool
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Pool Volume Calculator

Calculate the gallons of water in your swimming pool. Select your pool shape and enter the dimensions.

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Enter your pool dimensions above

Pool Volume Formulas

Use these formulas to manually calculate your pool volume:

Pool Shape Formula
Rectangle Length × Width × Avg Depth × 7.48
Circle Diameter × Diameter × Avg Depth × 5.9
Oval Length × Width × Avg Depth × 5.9
Kidney Length × Avg Width × Avg Depth × 7.48 × 0.85

Note: Results are in gallons. One cubic foot = 7.48 gallons.

Common Pool Sizes

Inground Pools

Size (ft) Avg Depth Gallons
12 × 24 5 ft 10,800
15 × 30 5.5 ft 18,500
16 × 32 5.5 ft 21,000
18 × 36 6 ft 29,000
20 × 40 6 ft 36,000

Above Ground Pools

Size Depth Gallons
15 ft round 48 in 4,978
18 ft round 52 in 7,646
24 ft round 52 in 13,594
12 × 24 oval 52 in 6,797
15 × 30 oval 52 in 10,620

Why Pool Volume Matters

  • Chemical dosing - All pool chemicals are dosed based on gallons
  • Equipment sizing - Pumps, filters, and heaters need to match your pool size
  • Fill time - Know how long it takes to fill or top off your pool
  • Water costs - Estimate your water bill for filling
Fiberglass kidney-shaped swimming pool in a backyard
Kidney and freeform pools use an average-width adjustment for a close estimate.

Getting a Measurement You Can Trust

The question I hear most is simply "how many gallons is my pool?" and the honest answer is that it lives or dies on your average depth. I've watched people measure length and width perfectly, then guess the depth and end up 3,000 gallons off. Walk the shallow end and the deep end with a tape or a marked pole, average the two, and this pool gallon calculator will hand you a number you can actually build your chemistry around.

If you've inherited a pool and have no idea of its size, this doubles as a quick pool size calculator. Measure the water surface, estimate the depths, and you'll have a working figure in under five minutes. I always jot that number somewhere I can find it, because I reach for it constantly when I'm dosing chemicals.

For anything irregular, treat the pool water calculator as a strong estimate rather than a survey. Break a wild freeform shape into a rectangle plus a rough oval, run each through the tool, and sum them. It's close enough for chemistry and equipment sizing, which is what the number is really for.

Frequently Asked Questions

How many gallons is my pool?
Measure your length, width, and average depth in feet, then use the right formula for your shape. A 16 × 32 rectangle at 5.5 ft average depth holds about 21,000 gallons. The pool gallon calculator above does the math for you once you enter your measurements.
How do I figure out my pool size?
Grab a tape measure for length and width, then measure the depth at the shallow and deep ends. This pool size calculator only needs those numbers plus your shape to give you an accurate gallon count.
How do I calculate average depth?
Add the shallow-end depth to the deep-end depth and divide by two. So a pool that's 3 ft shallow and 8 ft deep has an average depth of 5.5 ft. Getting this right is the single biggest factor in an accurate volume.
Why does knowing my pool's gallons matter?
Every chemical dose, pump, filter, and heater is sized by gallons, so an accurate number keeps your water balanced and your equipment right-sized. The pool water calculator gives you the figure you'll reuse for every dosing decision.
Is this pool water calculator accurate for irregular shapes?
For kidney and freeform pools it gives a close estimate using an average-width adjustment. If your shape is very unusual, break it into simple sections, calculate each, and add them together.