Before buying an air conditioner, you have to make the AC tonnage calculation. Not sizing an AC unit properly can cause $100s in wasted unit costs or future electricity costs.
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According to the DOE,
“…an air conditioner generally needs 20 BTU for each square foot of living space.”
We need to convert BTU to tonnage. 1 ton equals 12,000 BTU. That means that, on average, we will need 0.0016 tons per square foot.
To properly get the tonnage of the AC you need, you can use the AC tonnage calculator here:
For example, a standard 1,500 sq ft house would need a 2.5-ton air conditioner. To help us out, here is a quick table showing how many tons (and BTU) air conditioners we need for certain square footage:
|600 sq ft||12,000 BTU||1 Ton|
|900 sq ft||18,000 BTU||1.5 Tons|
|1,200 sq ft||24,000 BTU||2 Tons|
|1,500 sq ft||30,000 BTU||2.5 Tons|
|1,800 sq ft||36,000 BTU||3 Tons|
|2,100 sq ft||42,000 BTU||3.5 Tons|
|2,400 sq ft||48,000 BTU||4 Tons|
|2,700 sq ft||54,000 BTU||4.5 Tons|
|3,000 sq ft||60,000 BTU||5 Tons|
|3,300 sq ft||66,000 BTU||5.5 Tons|
|3,600 sq ft||72,000 BTU||6 Tons|
Here is the most frequently asked question about tonnage, BTU, and area (square footage):
How Many Tons Of AC Per Square Foot? (Tonnage Per Square Foot)
Simple answer: You need 0.0016 tons of AC per square foot.
In short, if you’re looking to cool down a 600 sq ft area, you would need:
AC Capacity = 600 sq ft * 0.0016 tons/sq ft = 1 Ton
In general, for every 600 sq ft, you need 1 ton of AC. This is a general estimate.
You can use the ‘tonnage per square foot’ formula to calculate how many tons of AC you need. Here is the formula:
AC Capacity (Tonnage) = (INSERT AREA IN SQ FT) * 0.0016 tons/sq ft
You can insert the area and calculate how many tons of AC you need per certain square footage.
When you calculate the tonnage, you can check out several 1-4 ton mini-split air conditioners here:
Hope this helps. If you have any questions, you can pose them in the comments below.
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44 thoughts on “AC Tonnage Calculator: Insert Tons, Get Square Footage”
Based on the tables & calculations I can find online, my unit should be somewhere between 4.5 tons and almost 6 tons.
I would expect an under-spec’d system to run all the time just trying to keep up. But ours does not. We had an A/C service come out recently and he suggested that we add more return ducts.
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I am trying to grasp what the symptoms are when the unit is under-sized. I would have expected the unit to burn out long before now if it was working to too hard.
What am I missing?Reply
I bought a 15 year old two story home in Houston. My appraisal shows the house is 4300 sqft (2400 on first floor and 1900 on second floor). There’s high open ceiling from entrance all the way through the living room. Property faces west, so it gets a lot of evening sun in the front. The house has tall high ceiling glass windows in the back, but the morning sun in the back is partly shaded by high a ceiling patio. The house seems to have good insulation (but it is 15 years old). The house has the original system installed by the builder with two 3 ton units (Evaporator coils were changed in 2013). I am about to replace this system. Is this tonnage adequate for this house? Should I go to a 4 ton/3.5 ton combo or perhaps a 5 ton/4 ton combo? At what point do we run into the problems of an oversized AC?