BTU for Room Cooling Calculator

BTU/hr needed = ft² × climate factor (20-30 BTU/ft² for typical US climates).

Inputs

Add 600 BTU per extra person.

Result

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General calculation reads

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How to use this calculator

  • Enter room area.
  • Pick climate / sun exposure.
  • Add extra occupants beyond 2.

About this calculator

Room AC sizing follows the rule of thumb: 20-30 BTU per ft², adjusted for sun exposure, insulation, and occupants. Window units are typically 5-25k BTU/hr; central AC is sized in tons (1 ton = 12,000 BTU/hr). Oversizing causes short-cycling and poor humidity control; under-sizing means the unit runs constantly.

Frequently asked

How does climate affect this?+
Hotter / sunnier rooms need more cooling per ft². A south-facing room with big windows: 30+ BTU/ft². A shaded interior: 20 BTU/ft².
What if the room is under a hot attic?+
Add 10% to the BTU. Top floors need more cooling than ground floors.
Window AC vs central?+
Window: per-room sizing, simple. Central: whole-house Manual J calculation, ducts matter.
Why not just oversize?+
Oversize ACs cycle on/off too fast — can't remove humidity. Result: cold but clammy.
Climate zone matters?+
For window units, just sun exposure. For central AC, full Manual J — climate zone, infiltration, duct losses.

Related calculators

BTU for Room Heating Calculator
Heating BTU/hr = ft² × insulation factor × ΔT.
AC Tonnage Calculator (sqft OR BTU input)
1 ton = 12,000 BTU/hr cooling. Convert sqft → tons (rule-of-thumb sizing) OR BTU → tons (direct).
Furnace Size Calculator
Furnace BTU = ft² × climate-zone factor (30-60 BTU/ft²).
Heat Load Calculator (U-value method)
Heat loss = U × area × ΔT for each surface, summed.
Ductwork CFM Calculator
CFM (cubic feet per minute) = BTU/hr × 0.07. Used for sizing ducts.
Room Volume for HVAC Calculator
L × W × H = ft³. Used for air-change calculations and AC/heating sizing.

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