AC Tonnage Calculator

Estimate the air conditioner capacity for a space.

How the Math Works

The AC Tonnage Calculator uses a straightforward two-step conversion process. First, it calculates the total cooling capacity needed in British Thermal Units (BTU) by multiplying the room's area in square feet by a standard factor of 11.5 BTU per square foot. This factor accounts for typical ceiling heights and average insulation. The second step converts the total BTU requirement into tons, the unit used to rate air conditioner capacity, by dividing by 12,000 since one ton of cooling equals 12,000 BTU per hour. For example, a 200 sq ft room requires 2,300 BTU and equals approximately 0.19 tons.

Practical Applications

To use this calculator practically, first measure your room's length and width in feet and multiply these dimensions to get the total square footage. Input this area value directly into the calculator, which will automatically perform the mathematical conversion. If you're replacing an existing unit, compare your calculated tonnage with your current AC's rating to verify adequacy. Note that this calculation provides a baseline—rooms with high heat-generating appliances, large windows, or unusual configurations may require adjustments to the recommended size.

Day-to-Day Use

This calculation prevents costly mistakes when purchasing an air conditioner, saving you hundreds of dollars by avoiding units that are too small or too large. An undersized unit will struggle to cool your space, leading to discomfort and higher energy bills, while an oversized unit cycles on and off frequently, reducing efficiency and potentially causing moisture problems. By finding the right size, you ensure optimal comfort, maximum energy efficiency, and proper dehumidification throughout your cooling season.

Worked example

600 ft² → 12,000 BTU (1 ton).

FAQ