4x12 Metal Wall Vents: Free Area, Airflow and Duct Fit
A 4x12 wall vent has a free area of 12.9 square inches and a calculated airflow of 45 CFM, and it drops into a duct opening of 95.3 x 298.5 mm.
- Duct opening
- 3.75″ × 11.75″
- Metric
- 95.3 × 298.5 mm
- Best free area
- 12.9 sq in
- Comes in
- Flush Wall · Framed Wall
4x12 buys 16 percent more free area than the 4x10, 12.9 square inches against 11.1, on the same 95.3 mm duct width.
Free area and airflow at this size
| Product | Free area | Open | Airflow | Price | |
|---|---|---|---|---|---|
| Flush Wall Vent [Metal] | 12.9 sq in | 27% | ≈ 45 CFM | from $39.99 | View 4x12 |
| Framed Wall Vent [Metal] | 12.9 sq in | 27% | ≈ 45 CFM | from $39.99 | View 4x12 |
Free area is the open cross-section air actually passes through, not the outside of the cover. How we calculate it.
Measuring for this size
The rough opening is 95.3 mm by 298.5 mm, the same width as the 4x10, so stepping up only means lengthening the cut, but check for a fire block or a top plate at the end of the stud bay before you start.
Will a 4x12 fit a 3 1/4 by 12 inch wall stack?
Not without checking. Our 4x12 wall vent is built for a 95.3 mm by 298.5 mm rough opening, and 3 1/4 inches is 82.6 mm, so a stack at that width leaves the opening about 13 mm narrow. Measure the drywall opening rather than the duct itself, since the drywall cut is usually larger than the stack behind it.
How much more air does a 4x12 move than a 4x10?
About 16 percent. The 4x12 measures 12.9 square inches of free area against the 4x10's 11.1, which is 45 calculated CFM against 38. Both sit on the same 95.3 mm duct width, so the gain comes from two extra inches of perimeter down each long side of the ring.
Can the 4x12 be installed on a ceiling?
Yes. The Flush version is built for walls and ceilings and the figures do not change with orientation. On a ceiling, plan for the 298.5 mm length to cross a joist or a strapping run, which means heading the opening off with blocking rather than cutting straight through.
How do I measure for a replacement vent?
Measure the duct opening, not the old cover. Pull the existing vent out, measure the hole itself across the width and the length in millimetres, and match that to the duct dimension listed on this page. Vent sizes are named for the duct, so a vent called 4x10 has a face larger than 4 by 10 inches. Measuring the faceplate is the single most common reason a size arrives wrong.
What happens if I order the wrong size?
Email support@khansupply.co with your order number and the millimetre measurements of your opening, and we will work out which size actually fits and sort out the exchange. Every Khan Supply vent also carries a 2-year warranty against defects, which is separate from a fit exchange.
What does shipping cost?
Nothing. Shipping is free on every order across North America, on a single vent and on a 5-pack alike. You will get tracking by email once the order is on its way. If a vent arrives damaged, photograph the box and the part and email support@khansupply.co, Monday to Friday 9 to 5 ET, and we reply within one business day.
Every Khan Supply vent is all metal, not plastic, and ships free across North America with a 2-year warranty. If a size is wrong, email support@khansupply.co and we sort out the exchange. Mon-Fri 9-5 ET, one business day reply.
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