RPM Guidelines by Bit Size
Router speed must decrease as bit diameter increases. This is the most critical safety rule in routing.
Last updated: 2026-02-27
Router Bit Speed Calculator
Calculate optimal RPM for router bits based on diameter and material for safe, efficient routing.
RPM Calculation Bit Types Material Speeds Safety Guide
Router Bit Parameters
Recommended RPM
Enter bit parameters to calculate optimal RPM.
Never exceed bit's rated speed. Larger bits at high RPM create dangerous conditions. Always use proper safety equipment when routing.
Surface speed should be 8,000-12,000 FPM (feet per minute) for optimal cutting. Use our calculator to determine safe RPM for your specific bit.
How to Use This Calculator
- 1 Select Bit Diameter Choose your router bit diameter from 1/4 inch to 3-1/2 inches.
- 2 Choose Bit Type Select from Straight, Spiral, Flush Trim, Roundover, Cove, Chamfer, or Panel Raising.
- 3 Pick Material Select the material you're routing: Softwood, Hardwood, Plywood, or MDF.
- 4 Review RPM Get recommended RPM range, safety warnings, and speed adjustment tips.
Pro Tip: Larger bits = Lower RPM. Surface speed should be 8,000-12,000 FPM. A variable speed router is essential for any bit over 2 inches in diameter. Start low and increase speed if needed — listen for smooth operation.
| Bit Diameter | RPM Range | Notes |
|---|---|---|
| Up to 1" | 18,000-24,000 RPM | Small trim, edging, straight bits |
| 1" to 2" | 12,000-18,000 RPM | Profile bits, dados, rabbets |
| 2" to 3" | 8,000-12,000 RPM | Large profiles, panel raising |
| Over 3" | 6,000-10,000 RPM | Panel raising bits (table-mounted only) |
Always check bit manufacturer's maximum RPM rating. Never exceed it.
Surface Speed (FPM) = pi * Bit Diameter (in) * RPM / 12 Safety & Best Practices
Critical Safety Rules
Safety Rule: Larger Bits = Lower RPM
- Never exceed bit's rated speed
- Large bits at high RPM = dangerous rim speeds
- Variable speed router is essential for bits over 2"
- Start low, increase if needed, listen for smooth operation
Best Practices
- Use sharp bits — dull bits require more force and heat up
- Multiple shallow passes — safer and better finish
- Secure workpiece firmly with clamps or jigs
- Wear safety equipment — eye, ear, and dust protection
- Check bit balance — wobble indicates damage or wear
Glossary of Terms
Revolutions Per Minute — the speed at which the router bit rotates. Must be adjusted based on bit diameter for safe operation.
Feet Per Minute — the speed at which the outer edge of the bit travels. Optimal range: 8,000-12,000 FPM. Determines cut quality and safety.
A router with adjustable RPM settings. Essential for large bits (2"+) that require lower speeds. Most quality routers offer 8,000-24,000 RPM range.
Large diameter bit (3-3.5") used for creating raised panels in cabinet doors. Must be run at 6,000-10,000 RPM in a router table only.
The clamping mechanism that holds the router bit shank. Available in 1/4" and 1/2" sizes. 1/2" shank preferred for larger bits due to better grip and less vibration.
Routing in the same direction as bit rotation. Can produce smoother finish but increases kickback risk. Reduce speed and depth 50% when climb cutting.
Frequently Asked Questions
Why do larger router bits need lower RPM?
Because the outer edge of a larger bit travels faster at the same RPM. A 3" bit at 24,000 RPM has a rim speed of 18,850 FPM — far exceeding the safe 12,000 FPM limit. Reducing to 10,000 RPM brings it to a safe 7,854 FPM.
What happens if I run a router bit too fast?
Excessive speed causes dangerous rim velocities, overheating, burning, premature bit wear, and potential bit breakage. Large bits at high speed can also cause severe kickback and workpiece damage.
Do I need a variable speed router?
Yes, if you use bits larger than 1 inch diameter. Fixed-speed routers typically run at 22,000-24,000 RPM, which is too fast for large bits. Variable speed routers allow adjustment from 8,000-24,000 RPM.
How does material type affect router speed?
Harder materials (oak, maple) require slightly lower RPM or slower feed rates. Softwoods (pine, cedar) can handle higher speeds. MDF and plywood are more consistent and tolerate a wider speed range.
What's the difference between RPM and feed rate?
RPM is how fast the bit spins. Feed rate is how fast you move the router along the workpiece, measured in inches per minute (IPM). Both must be balanced — too fast feed = tearout, too slow = burning.
Can I use the same speed for all materials?
No. While the primary speed determinant is bit diameter, material hardness affects the optimal speed. Reduce RPM 10-20% for very hard woods, and you can increase slightly for softwoods and MDF.