Pool & spa project calculators
Water volume is the starting point for planning pool or spa treatment. Measure the inside water dimensions, estimate the volume for the shape, then use the result with product-specific dosing instructions. These calculators provide estimates; manufacturer capacity information and chemical labels take precedence.
1. Estimate the water volume
For a pool, choose the shape that best matches the basin and use average water depth where the bottom slopes. For a spa or hot tub, use inside dimensions and the actual water depth, not the outside shell height. Seats, steps, curved walls, and the waterline can reduce real capacity compared with a simple geometric estimate.
- Pool volume calculator — estimate gallons in rectangular, round, oval, or other pool shapes.
- Spa and hot tub volume calculator — estimate water capacity from spa dimensions and depth.
2. Use the volume with product directions
Water-treatment amounts depend on the product, current water test, and target level. Use the measured or estimated gallons with the product label and test-kit instructions; do not mix products or assume one treatment rate applies to every pool or spa.
- Pool and spa chemical calculator — estimate a treatment amount from water volume, product strength, and target change.
Keep estimates in context
A shape-based volume is a planning estimate, not a substitute for the capacity shown in the owner’s manual or by the pool or spa manufacturer. If a result differs substantially from that specification, check the dimensions and units before using it to plan chemical quantities.