Sauna heater size calculator
Enter your sauna room's inside measurements to estimate the electric heater size you need. This is for traditional saunas with a heater and stones; infrared saunas come with their panels already sized.
How the estimate works
- Room volume: length × width × height, in cubic feet.
- Base heater size: 1 kW for every 45–50 cubic feet, a common rule of thumb in the sauna industry.
- Glass: add about 1 kW for every 10 square feet of glass, since glass loses heat faster than insulated walls.
- Cold or poorly insulated rooms: add about 15%.
The rule of thumb and the adjustments come from SaunaKits.com's heater sizing guide. That's a retailer's rule of thumb, not a standard. Every heater maker publishes a room-volume range for each model, and that range is what to follow. Use this estimate to narrow your choices, then check the heater's spec sheet.
Common heater sizes by room volume
| Room volume (cu ft) | Typical heater size |
|---|---|
| 100–150 | 3 kW |
| 151–210 | 4.5 kW |
| 211–310 | 6 kW |
| 311–420 | 8 kW |
| 421–530 | 9 kW |
| 531–700 | 10.5 kW |
| 701–850 | 12 kW |
| 851–1000 | 14 kW |
| 1001–1200 | 15 kW |
| 1201–1400 | 18 kW |
| 1401–1600 | 20 kW |
Chart from SaunaKits.com, before adjustments for glass or cold rooms. Heaters of 6 kW and up typically run on 240V and are hardwired; see sauna electrical requirements.