Swamp Cooler CFM Calculator
Evaporative cooler sizing by air changes.
Enter your values
ⓘ Live results
Results
- Cooler size
- 6,400 CFM
- Air changes
- 30 ACH
- House volume
- 12,800 cu ft
- Relief opening area
- 8.5 sq ft of open window
- Water use estimate
- 2.6 gal/hour
Quick answer
Evaporative coolers are sized for 20-40 air changes per hour, far more than refrigerated air conditioning.
CFM = volume x ACH / 60
How to use the Swamp Cooler CFM Calculator
- 1Measure the conditioned floor area and ceiling height.
- 2Pick the climate band — drier and hotter needs more air changes.
- 3Open windows on the far side to give the air a way out.
Worked example
Using the values the calculator loads with:
Inputs
- Floor area1600 sq ft
- Ceiling height8 ft
- ClimateHot dry (30 ACH)
Results
- Cooler size6,400 CFM
- Air changes30 ACH
- House volume12,800 cu ft
- Relief opening area8.5 sq ft of open window
- Water use estimate2.6 gal/hour
Frequently asked questions
Why open windows?
Evaporative coolers push air in, so they need an exit path or the pressure kills airflow.
Does humidity matter?
Yes — above about 60% relative humidity the cooling effect largely disappears.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.