Calculate how many pieces of corner bead you need for the outside corners of a drywall job.
Usage Tip
Metal bead is the most durable; paper-faced bead is easier to set straight and resists cracking.
Buy bead at least as long as the wall height so each corner is one continuous piece.
What Is Corner Bead?
Corner bead is the rigid strip – metal, vinyl, or paper-faced – fastened to an outside drywall corner to give it a straight, durable edge. It protects the vulnerable corner from dings and provides a clean profile to mud and paint against. One length runs the full height of each outside corner, floor to ceiling.
Metal vs Vinyl & Other Types
| Type | Best use |
|---|---|
| Standard metal | Standard drywall corners |
| Vinyl | Moist areas (baths, basements) – will not rust |
| Bullnose | Rounded (softened) corners |
| Paper-faced | Crack resistance – paper bonds into the mud |
Metal is the contractor default – cheap and strong. Vinyl suits damp rooms because it cannot rust. Paper-faced (metal or composite core laminated to paper) resists cracking and is fast with a hopper or clincher. Bullnose creates the rounded corner look and needs matching bullnose for both legs plus special inside fittings.
Outside, Bullnose & Finishing Stages
Corner bead goes on outside corners (the ones that stick out); inside corners get paper tape instead. Finishing runs in stages: fasten the bead straight and plumb, then three coats of joint compound – a bedding coat, a fill coat, and a thin skim – each wider and feathered out past the last, sanding between. Bullnose corners follow the same stages but use the rounded profile and rounded inside corner pieces where walls meet.
Stock Length Optimization
Corner bead comes in 8, 10, and 12 ft sticks. You want the shortest stock that still covers the corner in one piece – one piece per corner avoids a butt joint that is hard to hide. Match the stock to the ceiling:
| Ceiling height | Corner bead needed (per corner) |
|---|---|
| 8 ft | 1 x 8 ft piece |
| 9 ft | 1 x 10 ft piece |
| 10 ft | 1 x 10 ft piece |
| 12 ft | 1 x 12 ft piece |
Buying 8 ft sticks for a 9 ft ceiling means a joint on every corner; buying 12 ft for an 8 ft ceiling wastes a third of every stick. The calculator picks the smallest stock that covers your height and counts the pieces.
Installation, Fasteners & Mudding
- Set the bead plumb and tight to both walls – a crooked bead shows through every coat.
- Fastening: screws or nails every 8-10 in down both flanges (or staples/clinch for paper-faced; some metal is set in compound).
- Wipe the first coat tight to the nose so the bead just shows, then build out in two more coats.
- Feather each coat 2-3 in wider than the last; sand lightly between.
- Check the corner with a level before mudding – fixing it after is a re-do.
Common Corner Mistakes & Repair
- Not plumb – the most common and most visible error.
- Too few fasteners – the bead flexes and the mud cracks.
- Joint in the middle of a corner – use one full-length piece instead.
- Over-building the mud – thick coats crack and need heavy sanding.
- Repair: for a dinged corner, cut out the damaged section, fasten a new piece, and re-coat – do not just skim over a crushed bead.
Frequently Asked Questions
How many pieces of corner bead do I need?
Usually one stock length per outside corner. Pick the smallest stock (8, 10, or 12 ft) that covers your ceiling height. Enter corners and height above.
What length corner bead should I buy?
The smallest that covers the corner in one piece – 8 ft stock for an 8 ft ceiling, 10 ft for 9-10 ft, 12 ft for 12 ft.
Metal or vinyl corner bead?
Metal for standard corners; vinyl for damp rooms since it will not rust. Paper-faced resists cracking.
What goes on inside corners?
Paper tape, not corner bead – bead is for outside (protruding) corners.
How is corner bead fastened?
Screws, nails, staples, or set in compound – about every 8-10 in down both flanges, kept plumb.
How many coats of mud over corner bead?
Three – a bedding coat, a fill coat, and a skim – each feathered wider and sanded between.
Related Drywall Calculators
Note: piece counts, stock lengths, and costs are planning estimates and vary by ceiling height, corner condition, product, and layout. Measure actual corner heights – ceilings vary and damaged or out-of-plumb corners may need extra material. Confirm the right bead type for the location and follow the manufacturer fastening and finishing instructions. General DIY guidance, not a professional specification.