# What Size Air Conditioner Do I Need?

A 5,000 Btu air conditioner can effectively cool a room that measures 100 to 150 square feet, according to a basic industry standard. But while using the room size is a good starting point when sizing an air conditioner, there are other factors to consider, such as the room's location, how much sun it gets and how many people use it. Therefore, the best way to choose an air conditioner capacity is to start with the room's square footage, and then make adjustments as needed for the specific space.

### Tip

Determine Btu capacity for an air conditioner based on the size of the room and other important criteria.

## The Importance of Proper Sizing

Air conditioners cool interior spaces by removing heat and moisture (humidity) from the air, and they have to do both to work effectively. If an air conditioner is too big for a given area, it will turn on for short periods, a condition called "short-cycling." This cools the air quickly, but the air conditioner doesn't run long enough to remove the moisture, leaving the air feeling damp or clammy and sometimes uncomfortably chilly. The flip side of this is an air conditioner that's too small. It will run for long periods, using a lot of electricity and possibly never cooling the room adequately.

## Room Size Calculations

Start your room size calculation by measuring the width and length of the entire space you intend to cool. Multiply the numbers to find the total square footage, or area; for example, a room that's 12 feet wide and 20 feet long has an area of 240 square feet. The chart below lists the standard recommended range of air conditioner capacity (in Btu) for various room sizes. These values assume that you're cooling a single, relatively open area and that the ceiling is a standard height of about 8 feet.

### Tip

Btu ratings are typically given for small- to medium-size air conditioners, including window (or "room") units, mini split heat pumps and portable air conditioners. Central air conditioner systems typically are rated in tons, or refrigeration tons (RT). One ton of refrigeration capacity is equal to 12,000 Btu.