Pool calculator

Measure the water, not the outer walls: length and width or diameter, plus shallow and deep water depths. A flat bottom uses the same depth twice. The tool uses area × (shallow + deep) / 2. This is appropriate for a flat or uniformly sloping bottom in these symmetric shapes; shelves, steps, irregular slopes and sloping walls require separate sections or a measured volume.

Ellipse means a true ellipse. Rounded rectangle means straight sides with two semicircular ends: area = (length − width) × width + π × width² / 4. Length is the overall length. A circle uses diameter, not radius. 1 m³ = 1000 L; 1 US gal = 3.785411784 L.

Optional chlorine calculation: enter measured and desired free chlorine in mg/L (approximately ppm in dilute pool water) and the product’s available chlorine as Cl₂ equivalent. Mass % gives grams of product; g/L gives millilitres. Do not enter sodium hypochlorite mass % as available chlorine or assume that a bare liquid percentage is g/100 mL. Changing the basis clears the product strength.

This is a theoretical mass balance: chlorine grams = max(0, target − measured) × m³. For example, 48 m³ and a 1.5 mg/L increase require 72 g available chlorine; 70 mass-% gives 102.857 g product, whereas 125 g/L gives 576 mL. These are arithmetic examples, not target or application recommendations. Chlorine demand, degradation, mixing and pH chemistry are not modelled; no acid dose can be derived from pH alone. Follow the actual product instructions and measure again. Zero water depth is allowed. Input limits are software limits; entries are not stored.