How many BTU do I need per square foot?

A general rule is 20 BTU per square foot. Adjust for ceiling height (above 8 ft), climate (hot climates need 10% more), insulation quality, sun exposure, and room type. Kitchens need an extra 4,000 BTU.

What is a ton of air conditioning?

One ton of air conditioning equals 12,000 BTU per hour. A 1-ton unit can cool about 400–600 sq ft depending on conditions. Most residential AC units range from 1 to 5 tons.

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BTU Calculator

Calculate the BTU needed to cool or heat any room. Adjust for insulation quality, climate, room type, and sun exposure to find the right air conditioner size.

Calculate BTU Required

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Insulation Quality

Climate Zone

Room Type

Sunlight Exposure

About the BTU Calculator

BTU (British Thermal Unit) measures the energy needed to cool or heat a space. The standard baseline is 20 BTU per square foot, but this varies significantly based on ceiling height, insulation, climate, and sun exposure. Kitchens generate substantial heat from cooking appliances, requiring an extra 4,000 BTU. One ton of cooling capacity equals 12,000 BTU per hour. To estimate how much an air conditioner will add to your electricity bill, try our Electricity Cost Calculator.

Oversizing an AC unit is a common mistake — a unit that's too large will cycle on and off frequently, failing to dehumidify properly and wearing out faster. Undersizing forces the unit to run continuously without reaching the setpoint. Always choose the closest standard unit size above your calculated BTU requirement. For home improvement projects alongside your HVAC upgrade, our Tile Calculator can help plan flooring renovations at the same time.

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