How to Measure a Floor Register, Plus the Full Size Chart
Nine out of ten sizing mistakes come from one error, measuring the old vent cover instead of the hole it sits in. This guide shows the right way to measure in under two minutes, then links every standard size we stock so you can go straight to the right register.
The one rule: measure the duct opening, not the old cover
Register sizes describe the duct opening in your floor. A 4x10 floor register fits a hole that measures 4 inches by 10 inches. The old cover's faceplate is always bigger than the hole, so measuring it will send you a size up and the new vent will not fit.
Measuring in three steps
1. Lift out the old vent. Most drop-in vents lift straight out. If it's screwed down, remove the screws first.
2. Measure the hole. Width and length of the opening in inches, to the nearest eighth. Measure in two spots per direction, old openings are rarely perfectly square, use the smaller reading.
3. Order that size. A 4x10 opening takes a 4x10 register. Our drop-in design sits flush into the opening, no screws, no adhesive.
Special situations
Rough or oversized cut around the hole? Our LuxeEdge line uses a wider flange that hides damaged edges and gaps.
Joist blocking one side? Our Joist Avoider models offset the drop-in box so the vent still sits centered. Send us a photo and we'll confirm the right one.
Wall and ceiling vents measure the same way, the hole in the drywall, not the old grille. Our two-part wall vents clamp into the opening with no visible fasteners.
Between sizes or an odd opening? We build custom size vents to any dimension in our Mississauga shop.
Floor register size chart
Every size below is stocked in our Classic flush drop-in line. The size is the duct opening it fits.
| Opening width | Stocked lengths |
|---|---|
| 2 inch | 2x10, 2x12, 2x14 |
| 3 inch | 3x10, 3x12, 3x14 |
| 4 inch | 4x8, 4x10, 4x11, 4x12, 4x14, 4x16, 4x20, 4x24, 4x30, 4x36, 4x48, and every inch in between up to 4x72 |
| 5 inch | 5x10, 5x12, 5x14 |
| 6 inch | 6x6, 6x8, 6x10, 6x12, 6x14, 6x20, 6x24, 6x30 |
| 8 inch | 8x8, 8x10, 8x12, 8x14, 8x20, 8x24, 8x30 |
| 10 inch | 10x10, 10x14, 10x24, 10x30 |
| 12 inch | 12x12, 12x16, 12x20 |
Half sizes and in-between lengths are stocked too, browse the full floor vent collection or search your exact size. If your measurement isn't listed anywhere, that's what our custom size program is for.
Common questions
My opening is 4 1/8 x 10. Do I order 4x10? Yes if the extra eighth is on one rough edge, our vents allow a little play and LuxeEdge covers more. If it's a true 4.25 or larger, go custom.
The old cover says 4x10 on the back. Can I trust it? Usually, but measure the hole anyway. Thirty seconds now beats a return shipment later.
Do wall return grilles size the same way? Yes, by the wall opening. Common return sizes like 6x24, 8x30 and larger are in the wall vent collection.
One more trick: match your floor
Once the size is right, you can make the vent almost disappear. Our floor matching designs accept a piece of your own flooring in the vent face.
