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Pool Water Volume Calculator
Calculate your pool volume in gallons or litres from its shape and dimensions.
Formula verified
3+ known-answer test cases
Last verified August 2026
Result
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How to use the Pool Water Volume Calculator
- Choose rectangular or round to match your pool shape.
- Enter length and width, or diameter, in feet.
- Enter a single average depth, or switch to shallow/deep end if your pool slopes.
- Optionally enter your fill hose or pump flow rate to estimate fill time.
- Select Calculate to see gallons, litres and cubic feet.
Formula
Volume by shape
Rectangular: length × width × average depth Round: π × radius² × average depth (then convert to requested units)
Worked example
Verified example
QA passed
Shape: Rectangular Length: 20 ft, Width: 10 ft, Average depth: 5 ft Volume = 10 × 20 × 5 = 1,000 ft³ Gallons = 1,000 × 7.48052 = 7,480.52 US gallons Result: 7,480.52 US gallons
Why this matters: Gallons drives every chemical dosing calculation — get the volume wrong and you over- or under-treat the water, which affects both cost and swimmer safety.
Common mistakes
- Using a single average depth on a heavily sloped pool instead of the shallow/deep split-depth option, which understates volume on pools with a steep slope.
- Measuring current water depth instead of the pool's built depth, which differ if the pool isn't filled to the top.
- Mixing up diameter and radius on a round pool — using radius where diameter is expected inflates the volume roughly 4×.
Frequently asked questions
How many gallons is my rectangular pool?
Multiply length × width × average depth in feet to get cubic feet, then multiply by 7.48 to convert to US gallons.
How do I find the average depth of a sloped pool?
Add the shallow-end depth and deep-end depth together, then divide by two. Use that figure as the average depth in the calculation.
How much chlorine do I need based on pool volume?
Dosing depends on the product and your target free-chlorine level. Use your calculated gallons as the input to the product label's dosing chart.
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