BTU Calculator

Estimate the cooling needs of a room or house. Find the right air conditioner size — from a window AC for a bedroom to a central unit for an entire home.

Unit System

Room Dimensions

Length (ft)

Width (ft)

Ceiling Height (ft)

Room Type

Insulation Quality

Climate Zone

Number of Occupants

Each additional person beyond 2 adds ~600 BTU

Additional Factors

wb_sunnyHeavy sun exposure (south or west facing windows)roofingTop floor or directly under roof/attickitchenLarge kitchen appliances nearby

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Enter room dimensions to calculate the recommended BTU cooling capacity.

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What is BTU?

BTU (British Thermal Unit) measures how much heat an air conditioner can remove from a room per hour. The higher the BTU, the more powerful the unit.

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Room vs. Whole House

Window AC units handle one room (5,000–18,000 BTU). Central AC systems handle entire homes and are rated in tons (1 ton = 12,000 BTU).

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Sizing Tips

An undersized AC won't cool properly. An oversized AC cools too fast without dehumidifying. Insulation, sun exposure, and occupancy all matter.