Ventilation Calculator

Find the required CFM for bathroom, kitchen, or whole-house ventilation.

REQUIRED CFM
— CFM
exhaust airflow

Usage Tip

For a bathroom, use 1 CFM per square foot or 50 CFM, whichever is greater (the HVI standard).

THE MATH
CFM = Volume × ACH ÷ 60
Where: Volume = Area × height  •  ACH = air changes per hour
• Bathroom fans: minimum 50 CFM (HVI)
• Round up to the next standard fan size
Scroll to Top

The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.