How to Measure a Floor Register (and What to Send Us for a Custom Size)
The golden rule: measure the hole, not the cover
Floor registers are sized by the duct opening, the hole in the floor that the register drops into. They are not sized by the decorative faceplate you see from above. The faceplate always overlaps the floor around the hole, so it's larger than the register's nominal size. A "4×10" register fits a hole about 4" × 10"; its faceplate is noticeably bigger.
If you measure the top of your old cover, you'll usually come out roughly a size too big, and the new register won't drop in.
What you'll need
- A tape measure or ruler that reads to 1/16"
- A flashlight
- A pencil and paper (or your phone's camera)
- A screwdriver, if your register is screwed down
Step-by-step: measuring a floor register
Step 1: Remove the old register
Most floor registers lift straight out. Some are held with screws through the faceplate. Take those out first. Set the old register aside; you'll want it later.
Step 2: Measure the width of the opening
Measure the short side of the hole, from inside edge to inside edge. Older openings are often not perfectly square, so measure in two places (near each end) and write down both readings.
Step 3: Measure the length of the opening
Measure the long side the same way, in two places.
Step 4: Use the smaller readings
If your two readings differ, use the smaller number. A register sized to the smaller dimension will still drop in. One sized to the larger dimension may bind.
Step 5: Check whether your vent sits flush
Most registers rest on top of the floor. Some sit flush, dropped into a recessed pocket cut into the floor around the hole. If yours is flush, also measure the width, length, and depth of that recessed pocket. If your register sits on top of the floor, you can skip this step.
Step 6: Measure the old register too (as a cross-check)
With the old register upside down, measure:
- The drop-in body: the part that goes into the hole
- The faceplate: the outer flange that sits on the floor
These help confirm your opening measurement and show how much overlap looks right in your room.
Step 7: Take photos
Take one photo straight down into the opening with the tape measure in frame, and one of the old register. Photos catch the details numbers miss: rounded corners, an off-center duct, or a floor transition next to the vent.
Common mistakes to avoid
- Measuring the faceplate instead of the hole. This is the number-one reason a new register doesn't fit.
- Trusting the size stamped on the old register. Openings get recut during flooring jobs, so the stamped size and the real hole may not match.
- Measuring only once. Old floors move, and openings drift out of square.
- Rounding up. If your opening is 3-7/8", don't call it 4". Send the actual number.
- Ignoring the floor surface. Thick carpet or a raised tile edge can change how a faceplate sits.
What to send us for a custom-size register
Our Custom Size Floor Vent Register is built from a few key dimensions you provide. We update the 3D model to your numbers, print it, and ship it. Please include:
- Vent cut-out width × length, measured inside edge to inside edge (smallest readings), to the nearest 1/16"
- Recessed pocket dimensions (flush vents only): if your vent sits flush in a recessed pocket, send the pocket's width, length, and depth, also to the nearest 1/16"
- Color: black, white, or any color you choose, including glow-in-the-dark
- Photos of the opening (with the tape measure visible) and of the old register
Our registers can be up to 6" wide, with no set length limit. They work best at 16" long or less; longer registers are case by case, so ask us first.
Production takes about 1–2 weeks because each register is made to order. If your color is in stock, we start printing right away; if not, we order the filament first, then print. If you need it sooner, reach out through our contact form.
Is a plastic register right for your spot?
Our registers are 3D printed in PLA plastic, which should handle the air that typical home floor supply vents put out. As noted on the product page, plastic will likely be weaker than metal or wood, and we don't recommend direct loading. A custom print is a great fit for odd-size openings along walls, under furniture overhangs, or in low-traffic areas. For large openings or vents in the middle of a walkway, where someone could step directly on the register, a metal register is the safer choice.
FAQ
Do I measure the old cover or the hole? The hole. The register size is the duct opening; the faceplate is always larger.
My opening is 4-1/8" × 10". Is that a 4×10? A stock 4×10 may fit if the extra 1/8" is on one rough edge. If you'd rather have a snug fit, send us your actual measurements and we'll size to them.
What size can you make? Up to 6" wide, with no set length limit. Best results are at 16" long or less; longer registers are case by case.
Can I return a custom-size register? No. Each register is custom-made to your measurements, so we can't accept returns. That's why it pays to measure carefully and send photos.
Does it include a damper? No. Our registers don't include dampers or louvers.
Ready to order?
Measure your opening, then order your custom-size floor register starting at $35. Questions about your measurements? Contact us with a photo and we'll help.
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