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:

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:

- Single Zone Mini Split ACs: 1 Ton or 12,000 BTU. Estimated square footage: 600 sq ft.
- Dual Zone Mini Split ACs: About 2 Tons or 24,000 BTU. Estimated square footage: 1,200 sq ft.
- 3-Zone Mini Split ACs: About 3 Tons or 36,000 BTU. Estimated square footage: 1,800 sq ft.
- 4-Zone Mini Split ACs: About 3 Tons or 36,000 BTU. Estimated square footage: 1,800 sq ft.
- 5-Zone Mini Split ACs: About 4 Tons or 48,000 BTU. Estimated square footage: 2,400 sq ft.

Hope this helps. If you have any questions, you can pose them in the comments below.

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?

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.