# How To Buy A Dehumidifier – Part Two

In the first part of our dehumidifier buying guide, we started you out some of the basic things you need to figure out before you start checking out dehumidifier reviews and spend good money on a unit. We showed you how to figure out humidity level, air changes per hour (ACH) and how to calculate your room’s square footage. Now we are going to turn those figures into a formula that will tell you exactly what size unit you need to buy.

Measure the height of your room, from floor to ceiling. Now take the square footage of your room and multiple it by the height of the room to get your room’s cubic footage. For example, if your square footage is 80 feet and the height of your room is 8 feet, then your cubic footage is 640 cubic feet.

Your CFM is the amount of airflow in cubic feet that you need in order to properly dehumidify your room. To determine this value, multiply the cubic footage of your room by the ACH and then divide by 60. For example, if your room is 640 cubic feet and your ACH is a 5, then multiply 640 by 5 and then divide by 60 (640×5=3200/60=53.3 cubic feet per minute) to get your CFM.

Determine How Much Moisture You Need To Extract From Your Room

How many pints of water you need to extract from your room depends on your ACH and your square footage. Use the guide below to determine how many pints of water you need your dehumidifier to extract from your room each day:

• ACH 6: 16 pints per 500 square footage. For each additional 500 square feet add an additional 7 pints
• ACH 5: 14 pints per 500 square footage. For each additional 500 square feet add an additional 6 pints
• ACH 4: 12 pints per 500 square footage. For each additional 500 square feet add an additional 5 pints
• ACH 3: 10 pints per 500 square footage. For each additional 500 square feet add an additional 4 pints

For example, if you have a room that is 500 square feet and you have an ACH of 6, then you need a machine that extracts 16 pints of water per day. However, if the room is 1000 square feet with an ACH of 6, then you need it to extract 23 pints per day.