10x30 Metal Wall Vents: Free Area, Airflow and Duct Fit
A 10x30 wall vent has a free area of 69.6 square inches and a calculated airflow of 242 CFM, and it drops into a duct opening of 254 x 768.4 mm.
- Duct opening
- 10″ × 30.25″
- Metric
- 254 × 768.4 mm
- Best free area
- 69.6 sq in
- Comes in
- Flush Wall · Framed Wall
10x30 is the size that proves the method, because our geometry returns 69.6 square inches and the free area we already publish for this exact vent is 69.65 square inches, so the calculation behind every figure on this site reproduces a shipped number to within 0.05 square inches.
Free area and airflow at this size
| Product | Free area | Open | Airflow | Price | |
|---|---|---|---|---|---|
| Flush Wall Vent [Metal] | 69.6 sq in | 23% | ≈ 242 CFM | from $99.99 | View 10x30.25 |
| Framed Wall Vent [Metal] | 69.6 sq in | 23% | ≈ 242 CFM | from $99.99 | View 10x30 |
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 rough opening is 254.0 mm by 768.4 mm, so this is a framed and headed opening rather than a retrofit cut. Run horizontally it crosses at least one stud framed at 16 inches on centre; run vertically it sits inside a bay but usually meets a fire block. The Flush version is labelled 10x30.25 against the Framed version's 10x30 for the same hole.
How do I know these free-area numbers are real?
The 10x30 is the proof. Our geometry calculation returns 69.6 square inches for this vent, and the free area we already publish for the same part is 69.65 square inches. The two agree to within 0.05 square inches, and every other figure on this site comes from the same calculation on the same drawings.
What does 242 CFM mean in practice?
It is the airflow that 69.6 square inches of free area passes at a face velocity of 500 feet per minute, which is a design assumption rather than a measurement. It is the largest figure in the Khan Supply line. The duct and the fan behind the vent decide what actually moves through it.
Can I retrofit a 10x30 into an existing wall?
Rarely without framing work. The opening is 254.0 mm by 768.4 mm. Run horizontally it crosses at least one stud framed at 16 inches on centre, and run vertically it fits inside a bay but usually meets a fire block. Treat it as a framed opening with a header, and confirm the wall is not load bearing at that point.
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