3x10 Metal Wall Vents: Free Area, Airflow and Duct Fit
A 3x10 wall vent has a free area of 10.3 square inches and a calculated airflow of 36 CFM, and it drops into a duct opening of 73 x 247.7 mm.
- Duct opening
- 2.87″ × 9.75″
- Metric
- 73 × 247.7 mm
- Best free area
- 10.3 sq in
- Comes in
- Flush Wall · Framed Wall
3x10 is the wall size fed by the 3-inch stacks that run between studs, and at 34 percent open it ties with the 4x8 as the most open wall vent we publish, on 10.3 square inches of free area and 36 calculated CFM.
Free area and airflow at this size
| Product | Free area | Open | Airflow | Price | |
|---|---|---|---|---|---|
| Flush Wall Vent [Metal] | 10.3 sq in | 34% | ≈ 36 CFM | from $36.99 | View 3x10 |
| Framed Wall Vent [Metal] | 10.3 sq in | 34% | ≈ 36 CFM | from $37.99 | View 3x10 |
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 3x10 wall vent is built for a 73.0 mm by 247.7 mm rough opening, which clears a stud bay framed at 16 inches on centre easily, but the old cover screwed to the drywall measures well over that. Take the hole, not the faceplate.
Can the 3x10 wall vent go on a ceiling?
Yes. The Flush Wall Vent is built for walls and ceilings, and the 3x10 figures hold in either orientation: 10.3 square inches of free area, 34 percent open, 36 calculated CFM. What changes is the install, because on a ceiling the fasteners carry the weight of the part.
What is the difference between the Flush 3x10 and the Framed 3x10?
In airflow, none. Both publish 10.3 square inches and 36 calculated CFM because they share the same duct and tray geometry, 73.0 mm by 247.7 mm over a 50.8 mm by 225.4 mm tray. The difference is the edge: the Framed version has a visible frame that hides the cut edge of the drywall, and the Flush version finishes into the drywall with no frame showing.
Is 36 CFM enough for a small bedroom?
That depends on the room's heat loss and the duct feeding it, not on the cover. The 36 CFM figure is what 10.3 square inches of free area passes at a 500 feet per minute face velocity, a standard design assumption. If a room runs short on air, the branch duct and the balancing damper are the usual causes.
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.
Not sure of your size? · All sizes and free-area figures · Every size we make