Sizing
CFM is a starting point.
A common baseline is roughly 1 CFM per square foot for typical bathrooms. High ceilings, long runs, enclosed toilet or shower compartments, restrictive fittings, and pressure losses change the real requirement.
Guided recommendation
Choose for your bathroom—not somebody else’s.
Six questions turn a crowded model lineup into a sensible starting point. No email. No fake precision.
Question 1
Before you buy
Three measurements save a return.
Write these down before comparing exact model suffixes.
- 01
Ceiling cavity depth
Measure framing and obstructions, not just the old grille.
- 02
Duct diameter and route
Check the full path and outside termination.
- 03
Available wiring
Count switched functions and conductors for fan, light, and controls.
Do not overlook
The replacement-air path.
A fan cannot exhaust air the room cannot replace. A tight door undercut can make even a capable fan underperform.