AC Tonnage Calculator

All construction tools

Calculate air conditioning capacity in tons and BTU for your home with precision.

Room Specifications

Units

Length (ft)

Width (ft)

Occupants

Number of Windows

Sunlight Exposure

Is it a Kitchen?

Cooling Capacity

Need to size your AC?

Enter your room dimensions and environmental factors to find the correct AC tonnage and BTU rating.

About this calculator

Overview

AC tonnage measures the cooling capacity of an air conditioner. One 'ton' of cooling is equal to 12,000 BTU (British Thermal Units) per hour. This measurement originated from the amount of heat required to melt one ton of ice in 24 hours. Proper sizing is crucial: an undersized unit won't cool effectively, while an oversized unit will short-cycle and fail to dehumidify properly.

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Pro Tips

If the room is very sunny, increase your capacity by 10%.
If the room is heavily shaded, you can reduce capacity by 10%.
A kitchen requires an additional 4,000 BTU because of appliances like stoves and ovens.
For every occupant beyond two people, add 600 BTU to the total.

Fun Facts

"The term 'ton' in AC sizing comes from the cooling power of 2,000 lbs (one ton) of ice melting in 24 hours."
"Modern AC units are about 30% to 50% more efficient than those made in the mid-1970s."
"Manual J is the standard method used by HVAC professionals to determine the exact heat gain and loss of a building."

Formula: BTU = (Area × 20) + (Occupants > 2 ? (Occupants - 2) × 600 : 0) + (Windows × 1000) + (Kitchen ? 4000 : 0); Tonnage = BTU / 12,000