How to calculate pool volume
Pool volume in gallons comes from the surface area times the average depth times a conversion factor for the shape:
- Rectangle: length × width × average depth × 7.48
- Round: diameter × diameter × average depth × 5.9
- Oval: length × width × average depth × 6.7
Average depth is the shallow end plus the deep end, divided by two. For a flat-bottom pool, the shallow and deep numbers are the same. This calculator does that math for you.
How pool chemical dosing works
Every dose scales with how much water you have, which is why volume comes first. The calculator uses standard per-10,000-gallon industry constants and scales them to your pool:
- Free chlorine: raised with 12.5% liquid chlorine (liquid shock).
- pH up: soda ash (sodium carbonate). pH down: muriatic acid (31.45%), which also lowers alkalinity.
- Total alkalinity up: baking soda (sodium bicarbonate). Down: muriatic acid.
- Calcium hardness up: calcium chloride (77% flake).
- Stabilizer up: cyanuric acid (conditioner).
Balanced ranges to aim for
- Free chlorine: 1 to 3 ppm (higher if stabilizer is high)
- pH: 7.4 to 7.6
- Total alkalinity: 80 to 120 ppm
- Calcium hardness: 200 to 400 ppm
- Stabilizer (CYA): 30 to 50 ppm
Chemical order matters: balance alkalinity first, then pH, then sanitizer. Retest after the pump has circulated for a few hours.