Picking a sauna heater is the one decision people get wrong most often. Too small and the sauna never gets hot. Too big and you have just added $2,000 to $3,000 in electrical work nobody warned you about, because the heater needs more power than your panel can give.
This free calculator tells you the right heater size for your room in seconds. Enter your dimensions (feet or meters, US or metric), plus glass area, uninsulated walls, and outdoor exposure. You get a recommended kW range, what voltage and circuit it needs, and a plain warning when a build is going to need an electrician and a bigger budget.
It's one tool from Sauna Guide, the honest home sauna buying guide: what it actually costs, what actually matters, what everyone gets wrong.
