6x10 Metal Floor Vents: Free Area, Airflow and Duct Fit
A 6x10 floor vent has a free area of 15.4 square inches and a calculated airflow of 54 CFM, and it drops into a duct opening of 148.9 x 251.9 mm.
- Duct opening
- 5.86″ × 9.92″
- Metric
- 148.9 × 251.9 mm
- Best free area
- 15.4 sq in
- Comes in
- Undermount
6x10 is the trunk-drop size for great rooms and main-floor trunk lines where a 6-inch-wide opening was framed in.
Free area and airflow at this size
| Product | Free area | Open | Airflow | Price | |
|---|---|---|---|---|---|
| Undermount Flush Floor Vent [Metal] | 15.4 sq in | 26% | ≈ 54 CFM | from $94.99 | View 6x10 |
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
6x10 is Undermount only and drops into a 148.9 mm by 251.9 mm opening, so it shares the 251.9 mm length of the 3x10 and 4x10 Undermount but needs the bay opened to nearly 6 inches wide, which normally means adding blocking rather than making a straight cut.
Is a 6x10 a real upgrade over a 4x10?
Not as big as the label suggests. The 6x10 Undermount measures 15.4 square inches against the 4x10 Undermount's 13.3, so 16 percent more free area for 50 percent more face. In calculated airflow that is 54 CFM against 46. Choose the 6x10 for proportion in a large room, not as an airflow fix.
Why is the 6x10 only 26 percent open?
Because percent open is free area divided by the nominal face, and the free area lives in the ring around the inner tray. Making a vent wider grows the face quickly and the perimeter slowly. The 6x10 holds more total free area than the 3x10, 15.4 square inches against 12.2, spread across double the face, so the percentage falls from 41 to 26.
Can I use a 6x10 floor vent as a return-air grille?
We do not recommend it. At 15.4 square inches of free area and 54 calculated CFM, this is sized as a supply outlet. Return grilles are normally sized for much lower face velocity and much larger free area, so a supply-sized vent on a return can be noisy and restrictive. Have your HVAC contractor size the return.
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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