CNC router feeds and speeds calculator
Enter spindle RPM, the number of flutes on your bit and a chipload, and get the feed rate to program. Pick a material and bit size to see a starting chipload range.
How to use this calculator
A router bit cuts by taking a small bite with each flute on every revolution. That bite is the chipload (also called feed per tooth). The feed rate that produces it is:
Feed rate = RPM × number of flutes × chipload
Example: 18,000 RPM × 2 flutes × 0.009 in = 324 in/min. In metric, 18,000 × 2 × 0.23 mm ≈ 8,280 mm/min.
Why it matters: if the chipload is too small, the bit rubs instead of cutting, heats up, burns wood, melts plastic and dulls quickly. If it is too large, the bit deflects, leaves a rough edge or snaps. Picking a chipload first and calculating the feed from it keeps both problems away.
The starting ranges shown come from the CNC Router Store chipload chart for solid-carbide spiral bits (inches per tooth, by material and bit diameter). They assume a rigid machine. Lighter hobby routers often can't reach those feeds, so the usual fix is to lower the RPM rather than the chipload, which keeps the bit cutting instead of rubbing.
Plunge rate is commonly set to roughly a third of the feed, and depth per pass to about the bit diameter in wood for a profile cut (less for small bits, plastics and aluminum). Always check the bit manufacturer's own chart for your exact series. Not running a CNC yourself? Post the job on The Spool List and let makers quote.
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Questions about this calculator
Should I change RPM or feed if my machine can't go fast enough?
Lower the RPM and keep the chipload. A fast spindle with a slow feed makes the chipload tiny, which rubs and burns. Lower RPM brings the required feed down to what the machine can manage.
How many flutes should I use?
Two-flute bits are the common default for wood and MDF. Single-flute (O-flute) bits clear chips better in plastics and aluminum, which reduces melting and chip welding.
Is the chart chipload right for my machine?
It is a starting point. Make a test cut in scrap, check the chips (they should be chips, not dust) and the edge, and adjust in small steps.