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Calculation Machine

Swamp Cooler CFM Calculator

Evaporative cooler sizing by air changes.

Reviewed by the Calculation Machine team · How we check our maths

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.

The formula

CFM = volume x ACH / 60

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Floor area1600 sq ft
  • Ceiling height8 ft
  • ClimateHot dry (30 ACH)

Result

  • 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

How to use the Swamp Cooler CFM Calculator

  1. 1Measure the conditioned floor area and ceiling height.
  2. 2Pick the climate band — drier and hotter needs more air changes.
  3. 3Open windows on the far side to give the air a way out.

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