Start with the heated room's volume, then account for glass, stone, brick, concrete and other uninsulated surfaces. Those surfaces increase the heating load, so raw cubic footage alone can understate the heater requirement.
Get my sauna recommendation →For a traditional sauna, calculate interior volume as length × width × height. Harvia's published guidance uses an average starting point of about 1 kW per cubic meter of sauna volume. It also says each square meter of stone, glass or similar uninsulated surface can add the equivalent of 1.2 m³ of sauna volume; non-insulated log interiors use a factor of 1.5.
That makes “effective volume” more useful than raw volume when a room has a glass door, large window, masonry or other heat-storing surfaces.
The estimate is a planning screen, not permission to buy any heater with the same nominal kW. Each manufacturer publishes an approved room-volume range and installation clearances for each heater. Your final selection should fall inside that model-specific range.
Multiply the finished interior length, width and height. Then account for heat-loss surfaces rather than relying only on raw cubic footage.
Yes. Glass and similar uninsulated or heat-storing surfaces can increase the effective heating load.
No. Use the estimate to narrow the field, then verify the exact manufacturer's approved room-volume range, clearances and electrical requirements.
Saunometry combines room dimensions, heat-loss surfaces, capacity, placement, sauna type, budget and priorities to produce a preliminary sizing result and product shortlist.
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