Swimming Pool Volume Calculator
Accurate pool volume is essential for correct chemical dosing — an error of even 10% means you'll consistently over- or under-treat the water, leading to algae blooms or unsafe chlorine levels. This calculator handles four pool shapes: rectangular (L × W × avg depth), round/circular (π × r² × avg depth), oval/elliptical (π/4 × L × W × avg depth), and kidney/freeform (approximated as 0.45 × L × W × avg depth). Enter shape, dimensions, and average depth (the average of shallow and deep end) to get total gallons, cubic feet, estimated fill time from a garden hose at 9 GPM, and chemical startup quantities: pool shock at 1 lb per 10,000 gallons, chlorine tabs for weekly maintenance, and stabilizer (cyanuric acid) to protect chlorine from UV degradation at 30 ppm per 4,000 gallons.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
How many gallons is a 16×32 pool?
A 16×32 rectangular pool with a 5-foot average depth holds approximately 19,200 gallons. With a shallow end of 3 ft and deep end of 8 ft, the average depth is 5.5 ft, giving about 21,100 gallons.
How long does it take to fill a pool with a garden hose?
A standard garden hose delivers about 9 gallons per minute (540 GPH). A 20,000-gallon pool takes about 37 hours, or roughly 1.5 days of continuous filling.
How much pool shock do I need to open my pool?
For initial pool opening or shock treatment: use 1 lb of calcium hypochlorite shock (68% available chlorine) per 10,000 gallons of pool water. For a 20,000-gallon pool, use 2 lbs. If the pool has been sitting (green algae visible), triple shock: 3 lbs per 10,000 gallons. Always add shock to water, not water to shock, and add at dusk to prevent UV degradation.
How do I calculate my pool's average depth?
For a pool with a gradual slope from shallow to deep end: average depth = (shallow end depth + deep end depth) / 2. For example, a pool that goes from 3 ft to 9 ft has an average depth of 6 ft. For a pool with a flat shallow area, then a slope, then a flat deep area, measure each section separately and weight by length.