Why gallons matter every week
Every chemical dose on a pool label is per 10,000 gallons, so an accurate volume is the difference between a clean pool and an algae bloom. The calculator handles rectangles (length × width × average depth × 7.48) and rounds (π × radius² × depth × 7.48) — use the average depth: a pool sloping from 3 to 8 feet averages 5.5.
Freeform pools: average it out
Kidney and L-shaped pools are estimated by splitting them into rectangles and circles, computing each, and adding. When in doubt, under-estimate volume slightly and adjust chemical doses upward gradually — overdosing a smaller-than-claimed pool is how liners get bleached.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- USDA Natural Resources Conservation Service — soil texture, bulk density and seeding rate guidance.
- US Geological Survey — mineral commodity data and aggregate density references.
- National Stone, Sand & Gravel Association — aggregate grading and product specification references.
Figures, formulas and reference tables last verified: 19 September 2026.