Why Use This Calculator?
Every chemical dose on the bottle assumes you know your pool's gallonage — guess wrong and the water swings green or stings. This calculator computes exact volume for rectangular pools (length × width × average depth) and round pools alike.
Average depth is the trick: measure the shallow end and the deep end and take the middle. A 3-to-6-foot pool averages 4.5 feet, not the deep end's number — the most common dosing mistake there is.
How It Works
- Pick the pool shape and enter the dimensions in feet.
- Use average depth: (shallow end + deep end) ÷ 2.
- Keep the gallon figure on hand for every chemical dose this season.
Frequently Asked Questions
How do I calculate my pool's water volume in gallons?
Rectangular: length × width × average depth × 7.48 (gallons per cubic foot). Round: diameter squared × average depth × 5.9. The calculator applies the right formula per shape.
Why does pool volume matter for chemicals?
Chlorine, shock, algaecide, and pH adjusters are all dosed per gallon. Twice the water needs twice the product — dosing by guesswork is why pools drift cloudy.
How accurate is the average depth method?
Very close for pools with a consistent slope. Freeform lagoon shapes are estimates — err slightly high on volume and adjust chemicals by test results.
Tips & Things to Watch
- Write your gallon figure on the filter lid — you'll use it every week.
- Kidney and lagoon shapes: split the pool into rectangles, sum them, then dose.
- Refilling after a drain? The same number tells you the fill-time estimate.