6x12 Metal Floor Vents: Free Area, Airflow and Duct Fit
A 6x12 floor vent has a free area of 17.4 square inches and a calculated airflow of 61 CFM, and it drops into a duct opening of 148.9 x 301.9 mm.
- Duct opening
- 5.86″ × 11.89″
- Metric
- 148.9 × 301.9 mm
- Best free area
- 17.4 sq in
- Comes in
- Undermount
6x12 is the size people choose for proportion in open-plan floors, and the numbers say so plainly: at 17.4 square inches it lands within a tenth of a square inch of the 4x12 Drop-In's 17.5, across a face 50 percent larger.
Free area and airflow at this size
| Product | Free area | Open | Airflow | Price | |
|---|---|---|---|---|---|
| Undermount Flush Floor Vent [Metal] | 17.4 sq in | 24% | ≈ 61 CFM | from $99.99 | View 6x12 |
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
6x12 is Undermount only and needs a 148.9 mm by 301.9 mm opening, the same length as the 4x12 and 50 mm wider, so an existing 4x12 hole has to be widened across the joist bay rather than lengthened along it.
If a 6x12 flows the same as a 4x12 Drop-In, why choose it?
For proportion. At 17.4 square inches the 6x12 Undermount is within a tenth of a square inch of the 4x12 Drop-In's 17.5, but it spreads that air across a face 50 percent larger. In wide-plank floors and open-plan rooms the 6-inch width simply looks right against the boards.
What duct opening does a 6x12 need?
148.9 mm by 301.9 mm. That is the same length as the 4x12 Undermount and 50 mm wider, so stepping up from a 4x12 means widening the cut across the joist bay rather than lengthening it. Widening normally needs blocking added underneath to carry the flange along both long edges.
Is 24 percent open low for a floor vent?
It is normal for a flush ring vent at this size. Percent open is free area divided by the nominal face, so a large face reports a lower percentage even when total free area is higher. The 6x12 carries 17.4 square inches, more than every Drop-In except the 4x12, while reading 24 percent.
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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