AC Tonnage Calculator: How Many Sq Ft Will AC Cool?

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. 

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:

Calculated Tonnage:

0.00 Tons

 

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:

Tonnage Table

Area (Square Feet): BTU Tonnage
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.

12 thoughts on “AC Tonnage Calculator: How Many Sq Ft Will AC Cool?”

  1. 12/19/2020
    I live in the Dallas, TX area
    My A/C unit is 3.5 tons
    We have 18″ and 9″ return ducts to the upstairs unit.
    My house was built by Ryland, square footage is 2661 and insulated well.
    Although there are hot & cold spots in the house, typically in rooms with large windows, our unit does not run all the time in winter or summer and has lasted 11 years so far.

    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.

    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
    • Hello Greg, you have sound reasoning. There are two potential symptoms of under-sized units: not sufficient cooling, and a shorter lifespan of the AC unit. Your cooling is sufficient and the modern ACs are made to last 20 years even if you run them on 100% all the time (regular maintenance is required). Given your situation, you will probably have very little symptoms of these sorts. In short, you’re not missing anything. Hope this helps.

      Reply
  2. 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?

    Reply
    • Practically, the tonnage is sufficient if your home was sufficiently cool in the summer. Theoretically, 1 sq ft requires, on average, 20 BTU. 4300 sq ft translates to 86,000 BTU, or about 7.2 tons. Add Houston climate, high ceilings, and subtract good isolation and you’re looking at about 8 tons.

      Oversized ACs are more expensive to buy and install; that’s the only major drawback. Hope this helps.

      Reply
    • Hello Joseph, according to EPA’s recommendation, you would need 20 BTU per 1 sq ft. That means about 20,000 BTU. 12,000 BTU equals 1 ton. The safe bet would be to buy a 2-ton unit (24,000 BTU in total).

      Reply
  3. I have a commercial space rented as a barbershop with aprox 6-7 workers at a time and about 6-10 customers in the shop at a time during peak hours. The space currently has a 6ton ac unit. The space is only 1200 sq ft and a floor to ceiling about 12ft. Will a 3.5-4 ton unit be enough to properly cool my shop?

    Reply
    • Hello Isa, 4 ton (48,000 BTU) unit should be theoretically enough to cool down spaces up to 2,400 sq ft. In practice, the Energy Star guide recommends that you add 600 BTU per person. Let’s say you have 17 people in the shop, that would be 17*600 BTU = 10,200 BTU. So, you still have about 38,000 BTU left; that’s more than enough to adequately cool down your shop.

      Reply
  4. Must a/c condensers be placed w/I 2 feet of house, or can they be more remote?
    I would like them placed away from the house, but do not know if that is possible without problems.

    Reply
  5. Could you help me with Line-set or AC refrigerant line sizes ??
    3 ton AC unit waiting for electric run of 30 amp 220volt , but some knuckle head ran a 20amp yellow romex and what seems to be about a 3/4 line set, could be smaller maybe a 5/8 line set
    on 2nd deck patio , 2 floor to be AC’d is about 1800 sq ft
    I think the line set is to small
    The electric is definitely to small
    Nameplate rating is 25.7 amps

    Reply
    • Hello Micheal, sure thing. Well, if you need a 30 amp, 25.7 amps won’t cut it. It’s hard to talk about the specific situation but a 3 ton AC usually has a 3/4 line set. Hope this helps.

      Reply

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