4x14 Metal Floor Vents: Free Area, Airflow and Duct Fit
A 4x14 floor vent has a free area of 17.3 square inches and a calculated airflow of 60 CFM, and it drops into a duct opening of 98.9 x 351.9 mm.
- Duct opening
- 3.89″ × 13.85″
- Metric
- 98.9 × 351.9 mm
- Best free area
- 17.3 sq in
- Comes in
- Undermount
4x14 is the long-throw size on a 4-inch branch, used to spread the same air across a wider opening in front of a large window, and it is one of five floor sizes only the Undermount covers.
Free area and airflow at this size
| Product | Free area | Open | Airflow | Price | |
|---|---|---|---|---|---|
| Undermount Flush Floor Vent [Metal] | 17.3 sq in | 31% | ≈ 60 CFM | from $94.99 | View 4x14 |
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
Only the Undermount is built in 4x14 and it needs a 98.9 mm by 351.9 mm duct opening, so a 4x12 hole is exactly 50 mm short and the extra length usually runs into a joist or a strapping line.
Why is there no Drop-In or 2-in-1 in 4x14?
The Drop-In and the 2-in-1 are built in 3x10, 4x10 and 4x12 only. The Undermount Flush Floor Vent runs the full eight-size range, and 4x14 is one of the five sizes only it covers. There is no raised click-in face at this length, so the Undermount is the part to order.
Does a 4x14 move more air than a 4x12?
Yes, about 13 percent more. The 4x14 Undermount measures 17.3 square inches of free area against the 4x12 Undermount's 15.3, which is 60 calculated CFM against 53. Both sit on the same 98.9 mm duct width, so the extra comes from two more inches of perimeter along each long side of the ring.
Can I extend a 4x12 cut into a 4x14?
Usually yes. The 4x14 needs 98.9 mm by 351.9 mm and the 4x12 Undermount opening is 98.9 mm by 301.9 mm, so the width is already correct and you need exactly 50 mm more length. That last 50 mm is often where a joist or a run of strapping sits, so check underneath before you cut.
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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