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ComfortCalc
A room-level version of the BTU rule of thumb — for sizing a single unit, not a whole-home system.
This calculator is scaled for sizing an individual window unit, portable AC, or space heater for one room — for a whole-home central system, use the HVAC Sizing Calculator instead, which works from total home square footage.
A room with high ceilings or lots of direct sun exposure needs more BTU capacity than this simple area-based estimate suggests — treat the result as a starting point and round up for rooms with those factors.
BTUs needed
5,000 BTU/hr
Use this for sizing a single window AC unit, space heater, or portable unit — for a whole-home system, see the HVAC Sizing Calculator.
What you entered
Apply the BTU-per-square-foot rule of thumb
200 × 25= 5000 BTU/hrConvert to tons of cooling (1 ton = 12,000 BTU/hr)
5000 ÷ 12,000= 0.4167 tonsResult
BTUs needed: 5,000 BTU/hr
A 200 sq ft room needs roughly 5000 BTU/hr of heating or cooling capacity.