Sauna heater sizing calculator
The standard sizing rule for traditional sauna heaters is 1 kW of heater power per 45 cubic feet of room volume. Rooms whose walls include concrete, tile, or glass need about 25 percent more, because those surfaces absorb heat. The calculator below handles your exact dimensions; a reference table of common room sizes follows it.
Your heater power
- Room volume
- 252 cu ft
- Recommended heater power
- 5.6 kW
Compare heater power across the full sauna database, then confirm the final sizing with the heater manufacturer's own chart; models vary.
Common room sizes at a glance
| Room (L x W x H) | Volume | Heater power | With concrete or glass walls |
|---|---|---|---|
| 4 x 4 x 7 ft | 112 cu ft | 2.5 kW | 3.1 kW |
| 4 x 6 x 7 ft | 168 cu ft | 3.7 kW | 4.7 kW |
| 5 x 7 x 7 ft | 245 cu ft | 5.4 kW | 6.8 kW |
| 6 x 6 x 7 ft | 252 cu ft | 5.6 kW | 7.0 kW |
| 6 x 8 x 7 ft | 336 cu ft | 7.5 kW | 9.3 kW |
| 8 x 8 x 7 ft | 448 cu ft | 10.0 kW | 12.4 kW |
Prices and specifications verified July 25, 2026, and re-checked weekly after that. How these numbers are checked.
Free guide: sizing and budgeting a home sauna
A fill-in worksheet covering room sizing math, the electrical checklist, indoor vs outdoor decisions, a full cost worksheet, and ten questions to ask the dealer.
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