4x10 Metal Wall Vents: Free Area, Airflow and Duct Fit
A 4x10 wall vent has a free area of 11.1 square inches and a calculated airflow of 38 CFM, and it drops into a duct opening of 95.3 x 247.7 mm.
- Duct opening
- 3.75″ × 9.75″
- Metric
- 95.3 × 247.7 mm
- Best free area
- 11.1 sq in
- Comes in
- Flush Wall · Framed Wall
4x10 is the default wall and ceiling register size, and it is the one buyers most often confuse with the 4x10 floor vent: same size label, different part, 11.1 square inches here against 13.3 and 14.8 on the floor versions.
Free area and airflow at this size
| Product | Free area | Open | Airflow | Price | |
|---|---|---|---|---|---|
| Flush Wall Vent [Metal] | 11.1 sq in | 28% | ≈ 38 CFM | from $36.99 | View 4x10 |
| Framed Wall Vent [Metal] | 11.1 sq in | 28% | ≈ 38 CFM | from $37.99 | View 4x10 |
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
A wall or ceiling vent is not rated to be stepped on, so if the opening is in a floor order a floor vent. In a wall, note that the 4x10 is built for a 95.3 mm by 247.7 mm rough opening rather than a full 101.6 mm by 254.0 mm cut.
Can I use the 4x10 wall vent in a floor?
No. Wall and ceiling vents are not built to be stepped on. If the opening is in a floor, order a floor vent: the 4x10 Drop-In or the 4x10 Undermount, which also carry more free area at 14.8 and 13.3 square inches against this vent's 11.1.
Why is the 4x10 wall vent 28 percent open when the 4x8 is 34 percent?
Because the 4x8 uses a wider slot on its long sides, 17.0 mm against the 4x10's 11.1 mm. The 4x10 still holds more total free area, 11.1 square inches against 10.8, but spreads it over a face 20 percent larger, so the percentage falls. Percent open compares shape, not capacity.
Flush or Framed for a 4x10 retrofit?
Framed, if the existing cut is oversized or ragged, because the frame hides the edge. Flush, if you are taping and mudding drywall anyway and want no visible border. The airflow is identical either way at 11.1 square inches and 38 calculated CFM, so this is purely a finish decision.
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