Work out btu for room size instantly with clear inputs, formula shown and shareable results.
Room sizing rules of thumb express cooling need as BTU per hour per square foot, with the rate set by how well the envelope resists heat: 20 for a well insulated room, 25 for average construction and 30 for poor insulation or heavy glazing. The result is corrected for ceiling height because the published rates assume 8 ft.
Room BTU
BTU/h = length x width x rate x (ceiling height / 8)
Tonnage
tons = BTU/h / 12000
BTU/h = length x width x rate x (ceiling height / 8). Room sizing rules of thumb express cooling need as BTU per hour per square foot, with the rate set by how well the envelope resists heat: 20 for a well insulated room, 25 for average construction and 30 for poor insulation or heavy glazing.
No. An oversized unit short-cycles, which cools the air without running long enough to remove humidity, leaving the room clammy and the compressor stressed.
This calculator takes 4 inputs: Room length, Room width, Ceiling height, Insulation quality. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.