Swimming Pool Volume Calculator

Swimming pool volume is the foundation for every chemical dosage calculation — chlorine, pH adjusters, alkalinity, calcium hardness, and shock treatments are all dosed per 10,000 gallons. Getting this number right is essential for safe, clear water.

Volume formulas by pool shape:

Rectangular pool: V = Length × Width × Average Depth × 7.48 (7.48 converts cubic feet to gallons)

Average Depth = (Shallow End Depth + Deep End Depth) ÷ 2

Oval pool: V = Length × Width × Average Depth × 5.9 (π ÷ 4 × 7.48 ≈ 5.9)

Round pool: V = π × (Diameter ÷ 2)² × Depth × 7.48 Or simplified: V = Diameter² × 5.9 × Depth

Kidney/freeform pool: Divide into geometric sections, calculate each, sum totals.

What each variable means:

• 7.48 — gallons per cubic foot (1 cubic foot = 7.480519 gallons)
• Average depth — the most misunderstood input; a pool with a 3-foot shallow end and 8-foot deep end has an average depth closer to 5 feet (not 5.5, because of the gradual slope)
• Actual vs. geometric volume — pool walls are typically vertical in the shallow end, then slope; true average depth may require 3–4 depth measurements and averaging

Reference: chemical dosing per 10,000 gallons:

• Chlorine shock (1 lb of calcium hypochlorite): raises free chlorine by ~5 ppm
• Muriatic acid (1 quart): lowers pH by ~0.2 units in 10,000 gal (varies with alkalinity)
• Baking soda (1.5 lbs): raises total alkalinity by ~10 ppm
• Calcium chloride (12.5 oz): raises calcium hardness by ~10 ppm

Worked example: Rectangular pool: 32 ft × 16 ft. Shallow end: 3.5 ft, deep end: 8.5 ft.

• Average depth = (3.5 + 8.5) ÷ 2 = 6.0 feet
• Volume = 32 × 16 × 6.0 × 7.48 = 3,072 × 7.48 = 22,978 gallons (~23,000 gallons)

To raise free chlorine by 3 ppm (a typical weekly shock):

• Pounds of calcium hypochlorite needed = (23,000 ÷ 10,000) × 3 ÷ 5 = 2.3 × 0.6 = 1.38 lbs
• Round to 1.5 lbs and add in the evening with the pump running.