Hot Tubs & Spas
8 free calculators — every one shows its formula and a worked example.
Hot Tub Alkalinity CalculatorBaking soda in teaspoons — and why most guides tell you 2.5× too much.Hot Tub Foam DiagnosticFoam has three causes — find yours instead of pouring defoamer.Hot Tub Filter ScheduleRinse, soak, replace — scaled to how hard your spa actually works.Hot Tub Chemical CalculatorEvery spa reading graded at once, with teaspoon doses and a drain date.Hot Tub Volume CalculatorYour spa's real gallons — seats lie, tape measures don't.Hot Tub Shock CalculatorSpa shock doses by the gram, chlorine or non-chlorine.Hot Tub Bromine CalculatorBromine granule doses in teaspoons, plus the fresh-fill startup routine.Hot Tub Chlorine CalculatorSpa-sized chlorine doses in teaspoons — small water, exact math.