Swamp Cooler CFM Calculator
Evaporative cooler sizing by air changes.
Enter your values
Enter the floor area in sq ft.
Enter the ceiling height in ft.
Choose one of: Mild (20 ACH), Hot dry (30 ACH), Very hot dry (40 ACH).
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Evaporative cooler sizing by air changes. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Floor area, Ceiling height, Climate |
| Main output | Cooler size |
| Formula | CFM = volume x ACH / 60 |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Floor area(sq ft)
- Enter the floor area in sq ft.
- Ceiling height(ft)
- Enter the ceiling height in ft.
- Climate
- Choose one of: Mild (20 ACH), Hot dry (30 ACH), Very hot dry (40 ACH).
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.
What do I need to enter into the Swamp Cooler CFM Calculator?
Just 3 values: floor area, ceiling height, climate. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Swamp Cooler CFM Calculator work out the answer?
Evaporative coolers are sized for 20-40 air changes per hour, far more than refrigerated air conditioning. It applies the formula CFM = volume x ACH / 60 and shows the working so you can check each step by hand.
Is the Swamp Cooler CFM Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.