Stove sizing calculator

The rule of thumb behind every "heats up to X sq ft" claim: a home needs roughly 25–35 BTU/h per square foot at design (coldest-day) temperature — less if it's tight and mild, more if it's leaky and cold. This calculator picks the factor from your inputs and turns it into the peak-output range to shop for.

What to do with the number

• Shop for stoves whose certified peak output lands near the top of your range — the certified output range appears on every StoveAtlas model page.
• Under ~35,000 BTU/h: start with small stoves and the small-cabin ranking.
• 35,000–55,000 BTU/h: the mid-size class — see the medium-home ranking.
• Above ~55,000 BTU/h: large-firebox stoves and the large-home ranking — or consider a furnace or boiler for whole-house distribution.
• Don't oversize. A stove that must smolder to keep the room livable burns dirty and builds creosote — the sizing guide explains why smaller-but-hotter beats bigger-but-choked.

Assumptions

BTU/h per square foot factors: mild climate 18–24 (good insulation) to 26–32 (poor); mixed climate 22–28 to 33–40; cold climate 27–34 to 40–48; "average" insulation sits between. These bracket the common 25–35 BTU/sq ft rule used across this site (see methodology). The result is a starting point at design temperature, not a heat-loss calculation — ceiling height, window area, floor plan openness, and how far the heat must travel all matter. For a real heat-load number, ask for a Manual J calculation.