Sauna Heater API
Sauna-heater sizing maths as an API, computed locally and deterministically — the heater-power, stone-mass and electrical numbers a sauna builder, installer or wellness retailer sizes a cabin with. The heater-size endpoint gives the power: about 1 kW per 1.3 m³ of well-insulated cabin (room volume ÷ 1.3), with cold surfaces the heater must also warm — a glass door or wall, bare stone, tile or uninsulated timber — adding roughly 1.2 m³ of equivalent volume per square metre, so a 10 m³ room with a 2 m² glass door wants about a 10 kW heater, rounded up to the next standard size. The stones endpoint gives the recommended sauna-stone mass, roughly 10–20 kg per kW (more stones for a softer, steamier löyly, fewer for a faster warm-up), with a note to use proper peridotite/olivine stones stacked loosely. The electrical endpoint gives the current the resistive heater draws — power ÷ voltage for single-phase or ÷ (√3 × voltage) for three-phase, since most heaters above ~4 kW are wired three-phase to keep the per-leg current and cable size down — to size the breaker and the dedicated RCD-protected circuit. Everything is computed locally and deterministically, so it is instant and private. Ideal for sauna and wellness retailers, home-improvement and DIY tools, and HVAC/electrical estimating apps. Pure local computation — no key, no third-party service, instant. Estimates — follow the heater maker's chart and local wiring code. 3 compute endpoints. For steam-boiler maths use a boiler API; for room heat loss a U-value API.
api.oanor.com/saunaheater-api
