Roundover Router Bit Sizes: Match Radius to Project
By Premium CNC & Router Bits for Precision Cutting | Published: 2026-10-30
Category: Buying Guides
Learn how to choose the right roundover router bit size for your woodworking project, from small 1/8" radius to large 7/8" radius bits.
Quick Answer
Choose a roundover bit radius that matches the edge thickness you want to soften: 1/8" for light chamfer-like rounding on thin stock, 5/16" for a medium profile on cabinet doors, 3/4" for heavy bullnose edges on tabletops, and 7/8" for large decorative edges on substantial moldings.
Why Radius Size Matters
The radius of a roundover bit determines how much material is removed from the edge and how pronounced the curve appears. A small radius (1/8" or 5/16") creates a subtle softening that still leaves most of the edge visible. A large radius (3/4" or 7/8") removes more material, producing a bullnose-like profile that reduces the apparent thickness of the workpiece.
Using the wrong radius can ruin the look of a project. A 1/8" bit on a thick tabletop will barely round the edge, while a 7/8" bit on a 1/2" board will cut away the entire edge thickness. Match the radius to both the material thickness and the desired visual effect.
Trade-offs Between Small and Large Radii
Small radii (1/8" and 5/16") are versatile for general edge finishing. They work on thin stock where a large radius would cut too deep, and they leave a crisp, clean look. However, they do little to protect corners from dings on heavy-use surfaces like workbenches or countertops.
Large radii (3/4" and 7/8") create a more dramatic, rounded edge that feels smooth to the touch and hides minor imperfections. The trade-off is that they require thicker stock—at least as thick as the radius—and they remove more material, which can weaken a narrow board. They also require a slower router speed (10,000 RPM for the 7/8" bit) to avoid burning the wood.
Decision Rules for Choosing Roundover Radius
- Stock Thickness Check: The workpiece thickness must be at least equal to the roundover radius. For a 3/4" radius bit, use stock at least 3/4" thick. For a 7/8" radius, use stock at least 7/8" thick. Measure your material thickness before buying. A 7/8" bit on 3/4" stock will cut through the edge.
- Desired Edge Profile: For a light, chamfer-like softening, choose 1/8" or 5/16". For a medium bullnose that still shows a flat face, choose 3/4". For a full, heavy bullnose that dominates the edge, choose 7/8". Test on scrap first. The profile looks different on wood than on paper.
- Router Speed Compatibility: Large-diameter bits (3/4" and 7/8" radius) require slower speeds (10,000 RPM). Small bits (1/8" and 5/16") run at higher speeds (16,000 RPM). Check your router's speed range before selecting a bit. If your router only runs at 20,000+ RPM, stick with 5/16" or smaller radii to avoid burning.
- Shank Size and Router Collet: Most large roundover bits have a 1/2" shank for stability. Smaller bits may have a 1/4" shank. Ensure your router collet matches the shank diameter. If you have only a 1/4" collet router, choose bits like the 5/16" radius with a 1/4" shank.
Roundover Router Bits We Recommend
- 7/8″ Roundover Router Bit – Whiteside 2011: 7/8 inch radius, 1-1/8 inch cut length, 1/2 inch shank, recommended RPM 10,000, made in USA. This large radius bit is ideal for heavy moldings and thick tabletops where you want a pronounced, smooth bullnose edge. The low RPM requirement means you need a variable-speed router.
7/8″ Roundover Router Bit – Whiteside 2011 - 3/4″ Roundover Router Bit – Whiteside 2010: 3/4 inch radius, 1-1/8 inch cut length, 1/2 inch shank, recommended RPM 10,000, made in USA. A slightly smaller large-radius option that still delivers a substantial roundover on 3/4" or thicker stock, perfect for countertops and furniture edges.
3/4″ Roundover Router Bit – Whiteside 2010 - 1/8″ Roundover Router Bit x 1/2″ Shank – Whiteside 2005C (AstraHP Coated): 1/8 inch radius, 1/2 inch cut length, 1/2 inch shank, AstraHP coated, recommended RPM 16,000, made in USA. The smallest radius in the Whiteside lineup, this bit is perfect for delicate edge softening on thin stock like plywood or 1/4" panels. The AstraHP coating reduces heat and friction for cleaner cuts.
- 5/16″ Roundover Router Bit – Whiteside 2002 (AstraHP Coated): 5/16 inch radius, 1/2 inch cut length, 1/4 inch shank, AstraHP coated, made in USA. A medium-small radius that works well on cabinet doors and drawer fronts. The 1/4" shank fits most trim routers, making it a good choice for portable routing.
Which Roundover Radius Fits Your Project?
Best For
- 1/8" radius: Light edge softening on thin stock (1/4" to 1/2" thick) like plywood, trim, and small boxes.
- 5/16" radius: Medium-profile rounding on cabinet doors, drawer fronts, and furniture panels.
- 3/4" radius: Heavy bullnose edges on countertops, tabletops, and 3/4" thick furniture.
- 7/8" radius: Large decorative edges on thick moldings, bar tops, and substantial tabletops.
Not For
- 1/8" radius: Not suitable for thick stock where you want a pronounced edge; the rounding will be barely visible.
- 5/16" radius: Avoid on very thin stock (under 1/2") where it may cut into the face.
- 3/4" radius: Do not use on stock thinner than 3/4"; the bit will cut through the edge.
- 7/8" radius: Not for standard 3/4" stock or any material under 7/8" thick.
