CFM & Grille Sizer
Estimate a planning airflow from room size, then find the grille that carries it.
Loading airflow data…
Total airflow is split evenly between them.
5.0
Default comes from the room type. Override for tight or leaky construction.
500 FPM
Selection aims for this. For the same grille and configuration, a lower catalog velocity generally means less grille-generated noise. Air reach depends on the product’s published throw data, which is not available for every model.
Measure the duct opening in the wall, floor or ceiling, not the old faceplate.
The grille overlaps the opening on every side.
Lay-in ceiling diffusers connect to round duct. The 24×24 on the
box is the ceiling grid face, not the duct size.
Room airflow planning estimate
0
CFM total ·
0CFM per vent
0cubic feet
0sq ft floor
0CFM per sq ft
A grille does not create airflow. It only shapes and passes what the duct, damper and
blower already deliver. If a room is starved, a larger grille alone will not fix it.
This is a comfort estimate, not an ACCA Manual J load calculation.
Catalog velocity of the closest match
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Show the math and what it does not cover
Three ways to go
3 products · full size list belowThree specific products, each answering a different question. Every size that carries this airflow is listed below.
Sizes that carry this airflow
Sizes below are shown for a new opening. Products marked
Outside published data are not verified at this airflow and are listed for
size comparison only. Replacing an existing vent? Your opening size is fixed.
Find products for my opening instead →
Out of stock sizes
Grilles for this opening
Accessories and exhaust products
These fit the same opening but are not air terminals: dampers, dryer vents and
exterior wall vents. They are not part of the airflow calculation.
Nearest sizes
These do not fit your opening as-is. Using one means modifying the opening or the boot.
Whole-house list
| Room | Vent | Size | ACH | CFM | Vents | CFM each | |
|---|---|---|---|---|---|---|---|
| Total estimate | 0 | ||||||
Add each physical room once. The total is a room airflow estimate; it is not a
separate supply total plus a return total. Totals are a planning estimate and do not confirm
that your existing blower, ducts or returns can deliver this much air.
How this works. Airflow is estimated with the air-changes-per-hour method: room volume × ACH ÷ 60. Product selection uses each grille’s published effective area (Ak, an effective-area factor from the manufacturer’s own test method) from its airflow table, so catalog velocity is CFM ÷ Ak, not a generic free-area assumption.
What it is not. Not a load calculation, and neither a cooling nor a heating design airflow. Room-by-room design airflow comes from an ACCA Manual J load calculation, and the duct system that delivers it from Manual D. Catalog velocity is a comparison basis between products, not a sound rating; published NC values are not part of this data set. The velocity bands are a shopping target, not an engineering verdict.
- Choosing a selection results in a full page refresh.