What size swamp cooler do you need?
Calculate the exact CFM (airflow) required to cool your home efficiently. Works with all major brands.
Sizing Calculator
Find the perfect CFM rating for your home
Understanding Your CFM Results
Apartments, mobile homes, or homes under 1,200 sq ft. A single window or side-draft unit typically suffices.
Most 3-bedroom homes (1,200-2,000 sq ft). A standard roof-mounted or large window unit works well.
Homes over 2,000 sq ft may need a high-capacity unit or multiple units for even cooling.
Common Sizing Mistakes
Buying Too Small
An undersized unit runs constantly but never cools properly. You'll be uncomfortable AND waste energy.
Ignoring Ceiling Height
A 1,500 sq ft home with 10-foot ceilings has 25% more air volume than one with 8-foot ceilings.
Forgetting Exhaust
Evap coolers need open windows or dedicated exhaust vents. Without proper airflow, humidity builds up.
Wrong Climate Zone
Evap coolers work best under 50% humidity. In humid climates, they add moisture without cooling.
How is CFM Calculated?
CFM (Cubic Feet per Minute) measures how much air the cooler moves. Evaporative cooling works by replacing the air in your home every 2-3 minutes. Our calculator uses the industry-standard Air Change Method:
We then adjust this base number based on your climate zone (humidity levels affect evaporative efficiency) and insulation quality (poorly insulated homes gain heat faster, requiring more airflow).
Frequently Asked Questions
Can I use one big cooler for my entire house?
Yes, if sized correctly and you have adequate exhaust (open windows or vents). A centrally-mounted roof unit with ductwork can cool an entire home. However, for very large homes (3,000+ sq ft), two smaller units often provide more even cooling than one massive unit.
What if my calculation is between two unit sizes?
Always round up. A slightly oversized unit can run on a lower speed setting (quieter, longer pad life), while an undersized unit will run constantly and never reach peak comfort. The energy difference is negligible.
Does CFM equal cooling power?
Not exactly. CFM measures airflow, but actual cooling depends on humidity. In dry climates (under 30% humidity), evap coolers can drop temperatures 15-25°F. In moderate humidity (30-50%), expect 10-15°F. Above 50% humidity, evap cooling becomes ineffective.
Why does insulation matter for sizing?
Homes with poor insulation gain heat faster from the outside. This means you need more frequent air changes (higher CFM) to maintain comfort. Well-insulated homes hold cool air longer, allowing for a smaller, quieter, more efficient unit.
Should I size based on whole house or just cooled rooms?
Calculate based on the rooms you actually want to cool. If you close off unused bedrooms, exclude that square footage. However, remember that cool air will naturally flow toward open areas, so factor in any connected spaces.
What's the difference between window and roof-mounted units?
Window units (3,000-5,000 CFM) are cheaper, easier to install, and great for single rooms or small homes. Roof-mounted (downdraft) units (4,500-6,500+ CFM) provide whole-house cooling through ductwork, are quieter inside, and don't block windows.