Router Bit Speed Calculator
The speed chart on your router is one number in disguise — a constant rim speed. A 3.5-inch bit at full speed is 14x a quarter-inch one.
The chart on the router is one number in disguise
Every router manual carries a table of maximum speeds by bit diameter, and it reads like a list of arbitrary limits. Convert each row to rim speed — how fast the cutting edge is actually travelling — and the table collapses to one figure.
| Bit | Published max | Rim speed |
|---|---|---|
| 1″ | 24,000 rpm | 6,283 ft/min |
| 2″ | 18,000 rpm | 9,425 ft/min |
| 2.5″ | 16,000 rpm | 10,472 ft/min |
| 3″ | 12,000 rpm | 9,425 ft/min |
| 3.5″ | 10,000 rpm | 9,163 ft/min |
Everything from 2 inches up sits between 9,163 and 10,472 — a 14% spread across the whole range. It is a constant rim-speed limit of about 9,500 feet a minute, written as a table because a table fits on a sticker.
The 1-inch row is the exception, and it explains itself: at full speed it reaches only 6,283. To hit the limit it would need 36,300 rpm, and a half-inch bit would need 72,600. No router spins that fast. Small bits are capped by the machine and big ones by the physics, which is exactly why the chart is flat at the small end and falls away as one over diameter at the big end.
The bit that looks slowest is spinning fastest
| Bit at 24,000 rpm | Rim speed | |
|---|---|---|
| 0.25″ | 1,571 ft/min | 26 ft/s |
| 0.5″ | 3,142 ft/min | 52 ft/s |
| 1″ | 6,283 ft/min | 105 ft/s |
| 2″ | 12,566 ft/min | 209 ft/s — over the limit |
| 3.5″ | 21,991 ft/min | 367 ft/s — over the limit |
At one router setting, a 3½-inch panel-raising bit has fourteen times the rim speed of a quarter-inch straight bit — 367 feet per second against 26. A big bit turns slowly enough to look harmless and its edge is moving faster than anything else in the workshop. That is the whole reason variable speed exists on a router.
Notes
- Follow the bit maker's figure over this one. The rim-speed limit here is fitted from published charts and is a good explanation of them, not a substitute. If a bit comes with a maximum printed on it, that number wins.
- Large bits belong in a table, not a handheld router. Anything over about two inches is a router-table bit. Spinning a panel raiser freehand is how people get hurt, whatever the speed dial says.
- Slower is not always better. Too slow burns the wood and dulls the carbide, because the edge dwells in the cut. The recommendation is a ceiling to stay under, not a target to sit at.
- Feed rate matters as much as speed. Rim speed sets what the router may do; how fast you move sets the chip load, and that is what actually determines burning, tear-out and edge life.
How to use
- Enter the bit diameter across the cutting circle.
- Set your router top speed if it is not 24,000 rpm.
- Read the dial setting, and whether the machine or the physics is binding.
- Follow the figure printed on the bit if it disagrees with this one.
Frequently asked questions
What speed should I run a router bit at?
Slow enough that the cutting edge stays under about 9,500 feet a minute. That works out at roughly 24,000 rpm for anything up to an inch, 18,000 at two inches, 12,000 at three and 10,000 at three and a half — which is exactly the chart printed on most routers.
Why do bigger bits need slower speeds?
Because what matters is how fast the cutting edge travels, not how fast the shaft turns, and rim speed is diameter times rpm. A big bit covers far more distance per revolution, so the same rpm sends its edge much faster.
Is the router speed chart arbitrary?
No — it is a constant rim-speed limit written as a table. Convert each published row and everything from two inches up lands between 9,163 and 10,472 feet a minute, a 14% spread across the whole range. One number, dressed as five.
Why is the small-bit row different?
Because the router runs out of speed before the physics does. A one-inch bit at full speed reaches only 6,283 feet a minute; to hit the limit it would need 36,300 rpm, and a half-inch bit 72,600. Small bits are capped by the machine, large ones by the physics — which is why the chart is flat at one end and falls away at the other.
How much difference does bit size really make?
At one router setting, a three-and-a-half-inch panel raiser has fourteen times the rim speed of a quarter-inch straight bit — 367 feet per second against 26. The big bit turns slowly enough to look harmless while its edge moves faster than anything else in the shop.
Can I run a large bit in a handheld router?
You should not. Anything over about two inches belongs in a router table regardless of speed — spinning a panel raiser freehand is dangerous even at the correct rpm.
Is slower always safer?
Safer, but not better. Too slow burns the wood and dulls the carbide because the edge dwells in the cut. Treat the recommendation as a ceiling to stay under rather than a target to sit at.
What about feed rate?
It matters as much. Rim speed sets what the router may do; how fast you move the work sets the chip load, and chip load is what actually decides burning, tear-out and how long the edge lasts.
Does this send anything anywhere?
No. Everything is calculated in your browser and nothing is stored or uploaded.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.