What Size Window AC Do I Need? A BTUs Guide

What are BTUs?

BTU stands for British Thermal Unit. It measures the cooling capacity of an air conditioner. The larger the room, the more BTUs you need to effectively cool the air.

The Danger of Oversizing

It's a common misconception to simply 'buy the biggest one'. If an AC has too many BTUs for a small room, it cools the air far too quickly and cycles off before it has a chance to extract humidity. This leaves the room feeling cold but uncomfortably clammy and damp.

The BTUs to Square Footage Guide

To calculate the right size, measure the square footage of your room (Length x Width). Then match it below:

• 100 - 150 sq. ft.: 5,000 BTUs
• 150 - 250 sq. ft.: 6,000 BTUs
• 250 - 350 sq. ft.: 8,000 BTUs
• 350 - 450 sq. ft.: 10,000 BTUs
• 450 - 550 sq. ft.: 12,000 BTUs
• 550 - 700 sq. ft.: 14,000 BTUs

Other Factors to Consider

Square footage isn't the only factor. You need to adjust your BTUs based on the room's environment:

• High Ceilings: Add 10% more BTUs for ceilings over 8 feet.
• Sunlight: If the room is heavily shaded, reduce capacity by 10%. If it gets direct blazing sun, increase capacity by 10%.
• Kitchens: Always add exactly 4,000 BTUs to a kitchen unit, because cooking generates massive amounts of heat.
• Room Capacity: If the room routinely has more than two people in it, add 600 BTUs per additional person.

Picking the perfect size ensures maximum cooling, proper humidity removal, and low electricity bills.