# How to Calculate What Size Central Air Conditioner You Need?

Finding the right air conditioner size is very important because each home is different, and the size of your central air conditioner will depend on various factors apart from the size of your house. These factors include your roof type, the height of the ceiling, number of windows, type of insulation, heat transfer of the walls etc. Usually, the size recommended in the manufacturer’s guidelines do not consider these factors and hence may be incorrect.

## What Size Central AC Do I Need?

Air conditioner sizes do not mean your unit's physical size. The size of an AC unit is expressed in tons which evaluate how much heat it can remove in an hour. For example, a typical AC unit is one ton and it cools 12000 BTU/hour. Here, BTU is a measure of heat. If you look at how many BTUs are needed to cool a bedroom or home office with the area around 100-300 square feet, it will come around 5000-6000 BTUs.

## Why Size Matters?

Size matters because a correctly sized air conditioner will run a proper full cycle and ensure that your home remains cooler longer. If the air conditioner is too small, then it will have to run non-stop for keeping your home adequately cool during the summer. This will increase your electric bills drastically. If the air conditioner is too big, then it cools the area too quickly, causing it to run for very short cycles. In such cases, the unit is unable to remove the humidity from the air properly, which can create mold and fungus problems. Also, excessive on-off cycling will wear out your air conditioner faster in such cases.

## How To Measure What Size Air Conditioner You Need?

To calculate the size of the air conditioner you need for a room, first, multiply the length of the room with its width. Then multiply it with 25 BTU to get the ample cooling for the room under different weather conditions. For example, if the room is 15 feet long and 12 feet wide, it comes to 180 square feet. Now multiply 180 by 25 BTU per square foot you get 4500 BTU which is the minimum cooling capacity of the air conditioner you should buy.

## Single-Room AC Size Calculator Chart

Below is a single-room air conditioner size calculator chart to help you out. Keep in mind that this chart is based on a room with one door, two windows and a ceiling height of 8 feet.

Room Size in Sq Ft BTUs Recommended
0-150 5000
150-200 6000
250-300 8000
300-350 10,000
350-400 12,000
400-450 14,000
450-500 15,000
500-600 18,000
600-700 20,000
700-800 22,000
800-900 25,000

## Central Air Conditioner Unit Size Calculator

In case you have a central AC, its size can be calculated by using different online AC size calculators. Input the size of the room in square feet along with whether you live in a hot climate or cold climate into the size calculator. You will instantly get the tonnage and the BTUs needed for your room.