Air-mover count from wall perimeter (one every 10–16 ft, angled to the surface), plus coverage for a wet ceiling.
The perimeter rule
A common S500 starting point is one air mover for every 10–16 linear feet of wall, angled 5–45° to the surface so air sweeps along it. Tighter spacing dries faster; start at the low end for a set drying goal and add units for high evaporation loads, offsets, and inside corners.
Wet ceilings and extra coverage
A saturated ceiling adds a large evaporation surface the perimeter count does not cover, so this calculator adds units based on floor area when you flag a wet ceiling. Reassess daily — pull units as materials dry to avoid over-drying and wasted power.
Frequently asked
How many air movers do I need per room?
A common rule is one air mover per 10–16 feet of wall perimeter, angled to the surface, plus extra units for a wet ceiling or high evaporation load. This calculator gives a low-to-high range from the room dimensions.
How should air movers be placed?
Set them along the walls, angled 5–45 degrees to the surface, so the airflow sweeps along the wet material in one direction around the room. Keep corners covered and avoid pointing units directly at each other.
Do I need more air movers for a wet ceiling?
Yes. A wet ceiling is a large evaporation surface the wall-perimeter count does not include, so add units based on the floor area — this calculator does that automatically when you check “wet ceiling.”
More free tools
This knowledge, built into the software
RestoredOS runs the whole job on the same field knowledge behind these tools — drying logs, moisture mapping, scope, and billing.