Free calculators, built honestly
Each tool does one real job from a premium iOS utility — free on the web, no sign-up, no tracking. The apps add the part that compounds.
PoolDose — pool & spa chemical dosing calculator
Exact chlorine, bromine and biguanide (Baquacil) doses for any volume —
stabilizer-aware targets, shock detection, pH & water balance.
Slab — concrete slab, footing & sonotube calculator
Cubic yards and bags for any pour — tape-measure entry (12' 6 1/2" parses),
waste factor, rebar grid, truck loads and cost.
MiteWindow — varroa treatment timing checker
Is now a legal treatment window? Temperature bands, honey-supers rules, brood
state and class rotation for Apivar, formic, thymol & oxalic — plus the seasonal mite wash
threshold (mites per 300 bees).