About Pool & Spa Calculations
Almost every pool number starts with one figure: volume in gallons. Chemicals are dosed per gallon, the pump and filter are sized by turnover, and the heater is rated against the water it has to warm. Get the gallons right and the rest of pool care falls into place. Get them wrong and you'll over- or under-dose every time you touch the water.
Volume comes from shape and average depth. A rectangle is length times width times average depth times 7.48 gallons per cubic foot. Round and oval pools use their own formulas, and a pool with a shallow and a deep end uses the average of the two, not the deepest point. That average-depth step is where most home estimates go wrong.
Dosing is simple arithmetic once you have gallons, but treat the chemicals with respect. Salt for a chlorine generator is added to hit roughly 3,000 to 3,400 ppm, poured in gradually as the pump runs. Muriatic acid lowers pH and alkalinity, and it's strong: always add acid to water, never water to acid, wear gloves and eye protection, and pour slowly with the pump on. These tools tell you how much, not how to skip the label or basic safety.
On the money side, an in-ground pool is a major project, and cost swings hard by region, size, material, and finish. The cost and loan tools give a planning ballpark, not a quote, so confirm with local builders. Run your volume first, then dosing and budget, and you walk into the season knowing your numbers.