How to Calculate CFM
What is CFM?
CFM Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
CFM = Area (sf) × Ceiling Height / Air Changes per Hour / 60
Step-by-Step Guide
- 1Calculate room volume, multiply by required air changes, convert
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
400 sf room, 9 ft ceiling, 6 ACH
Result
CFM = (400 × 9 × 6)/60 = 360 CFM
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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