// multi-utility computation suite · offline · instant · precise
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tool.fan-cfm-requirement Calculator
Calculates the CFM airflow required from a ventilation fan to achieve a target air change rate in a room, and selects the appropriate fan size. Bathrooms require 1 CFM per sq ft (minimum 50 CFM); kitchens need 100 CFM for cooktops under 400 BTU/hr.
Inputs
Room Length Ft
Linear measurement. Ensure consistent units: 1 m = 1,000 mm = 3.281 ft.
Room Width Ft
Horizontal extent perpendicular to the length.
Room Height Ft
Vertical measurement. For health calculators, typically standing height without shoes.
Air Changes Hr
Reference formula or conversion factor shown for context.
Results
required CFM
Reference formula or conversion factor shown for context.
room volume (ft³)
The computed three-dimensional volume.
air changes per hour
Sample size or count used in the calculation.
fan category
The classification bucket this result falls into based on the computed value and the applicable reference scale.
CFM = Vol × ACH / 60
Reference formula or conversion factor shown for context.