BTU stands for British Thermal Unit. In HVAC, it measures how much heat an air conditioner can remove from a room per hour. A higher BTU rating means the unit can cool a larger or hotter space.

How is the BTU calculated?

The base calculation is 25 BTU per square foot of room area. This is then adjusted upward for high ceilings (above 8 ft), direct sunlight, and more than 2 occupants (each extra person adds 600 BTU).

What does tonnage mean?

AC tonnage refers to the cooling capacity in tons of refrigeration. One ton equals 12,000 BTU/h. A 1.5-ton unit provides 18,000 BTU/h and suits rooms of roughly 700-1,000 sq ft.

How many BTU do I need for a 20m² room?

20 m² equals approximately 215 sq ft. At the standard 25 BTU/sq ft baseline, that is about 5,375 BTU. The calculator adjusts this for ceiling height above 2.4 m (8 ft), direct sunlight exposure, and additional occupants beyond two.

What is the difference between BTU and tons of refrigeration?

One ton of refrigeration equals 12,000 BTU/h. A 1-ton air conditioner removes 12,000 BTU of heat per hour and suits rooms of roughly 450-550 sq ft under normal conditions. Larger rooms require 1.5-ton, 2-ton, or multi-split systems.

Is BTU Calculator free and private?

Yes. BTU Calculator is completely free with no account required. All calculations run in your browser and nothing is uploaded or stored.

Does BTU Calculator work on mobile?

Yes. BTU Calculator is fully responsive and works in all modern browsers on desktop, mobile, and tablet.

BTU Calculator

About BTU Calculator

BTU Calculator estimates the cooling or heating capacity required for a room based on its area, ceiling height, sunlight exposure, and number of occupants. Results are shown in BTU/h, kilowatts, and AC tonnage. The base formula uses 25 BTU per square foot, adjusted for high ceilings (above 8 ft), direct sunlight, and extra occupants beyond two. As a general rule, a room needs approximately 25 BTU per square foot. The calculator adjusts this baseline upward for rooms with high ceilings, strong direct sunlight, or more than two regular occupants. The result is shown in BTU/h, kilowatts, and AC tonnage to match the capacity labels used by HVAC manufacturers.

How to use BTU Calculator

Enter room area in m² or ft²
Set ceiling height, sunlight exposure, and number of occupants
See recommended BTU, kW, and AC unit type

Frequently Asked Questions

What is a BTU?: BTU stands for British Thermal Unit. In HVAC, it measures how much heat an air conditioner can remove from a room per hour. A higher BTU rating means the unit can cool a larger or hotter space.
How is the BTU calculated?: The base calculation is 25 BTU per square foot of room area. This is then adjusted upward for high ceilings (above 8 ft), direct sunlight, and more than 2 occupants (each extra person adds 600 BTU).
What does tonnage mean?: AC tonnage refers to the cooling capacity in tons of refrigeration. One ton equals 12,000 BTU/h. A 1.5-ton unit provides 18,000 BTU/h and suits rooms of roughly 700-1,000 sq ft.
How many BTU do I need for a 20m² room?: 20 m² equals approximately 215 sq ft. At the standard 25 BTU/sq ft baseline, that is about 5,375 BTU. The calculator adjusts this for ceiling height above 2.4 m (8 ft), direct sunlight exposure, and additional occupants beyond two.
What is the difference between BTU and tons of refrigeration?: One ton of refrigeration equals 12,000 BTU/h. A 1-ton air conditioner removes 12,000 BTU of heat per hour and suits rooms of roughly 450-550 sq ft under normal conditions. Larger rooms require 1.5-ton, 2-ton, or multi-split systems.
Is BTU Calculator free and private?: Yes. BTU Calculator is completely free with no account required. All calculations run in your browser and nothing is uploaded or stored.
Does BTU Calculator work on mobile?: Yes. BTU Calculator is fully responsive and works in all modern browsers on desktop, mobile, and tablet.

BTU Calculator

About BTU Calculator

How to use BTU Calculator

Frequently Asked Questions

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