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How Many Gallons Does Your Pool Hold?

Your pool gallons set the scale of every chemical dose. Measure the water’s dimensions and depth, then choose a shape below to estimate US gallons. Check those measurements before using the result for dosing.

Choose your pool shape

Rectangular (uniform depth)

For a level floor. Choose Rect (sloped) if the depth changes.

Confirm your inputs

Before you use a dose, compare every input with your fresh tests and measured pool volume. Confirm each example value only after you’ve checked it. When you change a value, you’ll need to confirm it again.

Volume Formulas by Pool Shape

  • RectangularGallons ≈ length (ft) × width (ft) × average depth (ft) × 7.48
  • RoundGallons ≈ π × radius² (ft²) × depth (ft) × 7.48
  • OvalGallons ≈ π × [length (ft) ÷ 2] × [width (ft) ÷ 2] × depth (ft) × 7.48
  • KidneyEstimated gallons ≈ [width A (ft) + width B (ft)] × length (ft) × average depth (ft) × 0.45 × 7.48A rough estimate from two widths; the curve of your pool can change the result.
  • L-ShapeGallons ≈ [arm 1 volume (ft³) + arm 2 volume (ft³)] × 7.48; exclude any overlap
  • Freeform / OtherUse a similar regular shape for a rough estimate, or measure the water added during a fill.

The volume formulas use 7.48 gallons per cubic foot to convert cubic feet to US gallons. Enter your lengths and depths in feet.

How to Measure Your Pool

  1. Length and width: use a tape measure at the water line. Measure the water area rather than the coping or deck.
  2. Depth: averaging the shallow and deep depths works only for a uniform wall-to-wall slope. For flat sections joined by a slope, choose “Rect (sloped)” and enter both flat lengths (0 if absent). For a 40 × 20 ft pool at 3–8 ft depth with a 25 ft shallow flat and no deep flat, the length-weighted depth is (25 × 3 + 15 × 5.5) ÷ 40 = 3.9375 ft: 40 × 20 × 3.9375 × 7.48 = 23,562 gallons.
  3. Above-ground pools: measure the actual waterdepth. Use your pool manual’s fill level, then measure the water instead of estimating it from the wall height.
  4. Round pools: measure the diameter across the center. The calculator divides it by two to find the radius.
  5. Freeform / kidney pools: treat a shape-based result as a rough estimate. During a planned fill, you can subtract the starting water-meter reading from the final reading. Other water use during that interval will also be counted, so keep it separate.

Why Pool Volume Matters

With the same water tests and chemical strength, more gallons means a larger calculated addition. Recheck your measurements when the water level or dimensions change. Before each treatment, use fresh water tests and your chemical’s label.

Confirm each measured dimension, then select “Save Pool Card” (or “Update Pool Card”). Your saved gallons will fill in on the other calculators, so you can carry the measurement into your next calculation.