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Every chemical dose starts here. Get the gallons right.
Every pool chemical instruction says "per 10,000 gallons" — which means every dose is wrong if your volume is wrong. This calculator computes exact volume from shape and dimensions: rectangles by length × width × average depth, ovals and rounds by proper ellipse and circle geometry, all converted at 7.48 gallons per cubic foot.
Pool owners use this once and write the number on the equipment pad forever: every chemical dose, shock treatment, and heater spec keys off gallons, and most owners are guessing within ±30%. Pool service techs use it on new accounts where the owner has no idea.
With a 3.5-ft shallow end and 8-ft deep end (5.75 ft average): 16 × 32 × 5.75 × 7.48 ≈ 22,000 gallons. A uniform 4.5-ft version of the same pool is about 17,200 gallons.
(Shallow depth + deep depth) ÷ 2 works for evenly sloped floors. If the pool has a flat hopper bottom or benches, take depth readings every few feet along the length and average them. When in doubt, err slightly low — overdosing chemicals is more dangerous than underdosing.