Hot Tub Calculator
With the hot tub calculator, you check your test strip and learn what chemicals to add, in which order, based on your tub size.
You can see what to add, and in what order, by answering three short questions.
Target levels for hot tub water
Your test strip targets are shown here in ppm (parts per million).
- Free chlorine levels
- 3 to 5 ppm
- Bromine, if that's what you use
- Aim for 4 to 6 ppm
- pH (still OK from 7.2 to 7.8)
- 7.4 to 7.6
- Total alkalinity levels
- 80 to 120 ppm
If the water smells bad or looks strange
Find the solution for what you see, including the right dose for your tub.
More hot tub calculator tools for heat and cost
Look at this before you buy or when the electric bill arrives.
Setup and ongoing care
These tasks repeat every few weeks or months.
How to read the strip consistently
After dipping the strip and holding it flat, compare the pads to the chart on the bottle at the time shown on the label. Check the pads in natural light instead of under the blue light from the tub.
Adjust alkalinity first, followed by pH, and then the sanitizer. Every adjustment affects the next, and the hot tub chemistry calculator tells you how much of each to add.