Hot tub calculators
Four tools that do the arithmetic so you do not have to. They run entirely in your browser, with no account and no signal needed once the page has loaded.
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Chemical dosing calculator
Volume plus a current reading and a target gives the exact ounces of pH up or down, alkalinity, chlorine, bromine, or shock to add.
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Water volume calculator
How many gallons your tub holds, from its shape and dimensions, with an allowance for seats and footwell.
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Filled weight calculator
How much your tub weighs filled with water and people, to check a deck or pad can take it.
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Running cost calculator
The monthly electricity to keep it hot, from size, temperature, cover condition, and your power price.
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Heat-up time calculator
How long it takes to heat from one temperature to another, given your heater size.
Start with the dosing calculator. If you do not know your gallons yet, the volume calculator works it out and remembers it for the others.