CNC Router Feed & Speed Calculator
Calculate feed rate, chip load or spindle RPM from the values you already have. The tool handles the arithmetic; you still choose starting values from the exact cutter manufacturer and validate them on your machine.
Feed rate, chip load and RPM calculator
Choose the value you want to solve for, then enter the other values from your cutter documentation or an existing setup. Results update automatically.
What this calculator does—and what it does not do
The arithmetic is straightforward: feed rate, RPM, flute count and chip load are linked. LMT Onsrud publishes feed rate as chip load × flutes × RPM and feed per tooth as feed rate ÷ (RPM × flutes). Amana Tool publishes the same relationships in its CNC feed/chip-load charts.
The difficult part is choosing the right starting values. Cutter geometry, material, tool diameter, axial/radial engagement, machine rigidity, spindle power, workholding and chip evacuation all matter. This tool therefore calculates the relationship you ask for but does not invent a recommended chip load.
Use a cutter maker's chart as the starting point
Start with the exact cutter manufacturer's guidance for the material and operation. If the chart gives a chip-load range, enter the specific value you are evaluating. If it gives RPM and feed rate, switch the calculator to Chip load to see the resulting feed per tooth.
Then validate on the actual CNC. A setting that is mathematically consistent can still be unsuitable if the machine cannot maintain the feed, the workholding moves, chips are recut, the cutter chatters, or the depth/width of cut is too aggressive.
Surface speed is useful context, not a replacement for cutter guidance
If you enter tool diameter, the result also shows surface speed. For imperial inputs, the calculation follows the published approximation SFM = 0.262 × tool diameter in inches × RPM. For metric inputs, it uses circumference × RPM to show meters per minute.
Surface speed can help compare spindle-speed choices for a specific cutter, but it does not by itself establish the correct feed, chip load or depth of cut.
How to use the result without turning it into a guess
If you are starting from a cutter chart, keep the cutter diameter, material and operation matched to that chart. Enter the published chip load, your chosen RPM and the actual flute count to calculate feed rate. If the result is faster than your machine can maintain smoothly, do not simply lower feed and leave everything else unchanged; that also changes chip load. Revisit the cutter guidance and choose a combination the machine can actually execute.
If you already have a cut that behaves well and want to understand it, switch to Chip load. Enter the actual feed, RPM and flute count. That gives you a useful baseline to record alongside material, cutter, depth of cut and stepover. It is much more useful than remembering only “60 IPM worked” because the same feed rate means something different at another RPM or flute count.
Connect the calculation to the rest of the setup
Use the CNC Router Bits selector to choose the cutter family before calculating feed relationships. For material-specific machine limits, see Wood, Acrylic or Aluminum. Dust/chip removal and workholding still matter, so pair the result with the Dust Collection guide and the appropriate fixture strategy.
Formula sources
Frequently asked questions
What is chip load on a CNC router?
Chip load is the distance the cutter advances per cutting edge for each spindle revolution. It connects feed rate, spindle RPM and flute count, but the appropriate target still depends on the exact cutter, material, depth and width of cut, machine rigidity and chip evacuation.
How do I calculate CNC feed rate from chip load?
Use feed rate = RPM × number of flutes × chip load. This calculator performs that arithmetic in inches per minute or millimeters per minute using the values you enter.
Can this calculator tell me the correct chip load for wood or aluminum?
No. It calculates relationships between values; it does not choose a safe or optimal chip load. Start with the exact cutter manufacturer’s chart or technical guidance for the material and operation, then validate on your machine.
Why can the same chip load use different RPM and feed-rate combinations?
Because chip load is a ratio. If RPM increases while chip load and flute count stay the same, feed rate must increase proportionally to preserve the same feed per tooth.
Does the calculator account for depth of cut, stepover or chip thinning?
No. Those factors can materially change cutting load and recommended settings. The calculator intentionally stays with the basic published machining relationships rather than applying a universal correction that may not fit the cutter or toolpath.