CNC Chip Load & Feed Rate Calculator
Select a material, cutter diameter, flute count and RPM to estimate feed rate. Enter your machine's usable cutting feed to check whether the result is within that limit.
The feed your gantry holds while cutting, not the rapid speed. In grbl this is capped by the $110 and $111 maximum rate settings, and anything faster in the G-code is clamped silently.
Starting values only. Check the cutter manufacturer's data sheet and machine instructions, then confirm suitable settings with a supervised cut in scrap of the same material and thickness.
Use the calculator with your CAM settings
Choose the cutting diameter rather than the shank size, and use the flute count and spindle speed from your planned operation. The material and diameter selectors choose a preset; check that displayed target against your cutter's own data before using the result.
For the reference ranges and formula behind these presets, use the CNC chip load chart for wood.
Read the machine-limit result
A reachable result means the calculated feed is at or below the limit you entered. It does not confirm that the machine can hold that feed through every corner or that the cutter can handle the operation. An out-of-reach result includes an approximate RPM needed at your entered feed limit.
Check any suggested RPM against the spindle and cutter instructions before changing it. For the machine specifications that constrain those choices, see the desktop CNC router buying guide for woodworking.
Before transferring results to CAM, review your router bit geometry and climb vs conventional milling direction.
Calculator frequently asked questions
- What feed rate does this give for a 1/4-inch bit in plywood?
- Select MDF and plywood, 1/4 inch, two flutes and 18,000 RPM. The calculator uses its 0.015-inch preset and displays 540 IPM. With a 150 IPM machine limit, the result is out of reach. This is an example of the calculator's preset, not a setting approved for every plywood cutter.
- Why is the calculated feed rate higher than my machine can move?
- The calculated target is compared with the usable cutting feed you entered; it is not capped to that limit. Try a lower RPM within the spindle and cutter's permitted range, or recalculate for a suitable cutter with fewer flutes. If the displayed RPM needed is outside the equipment's supported range, the preset is not reachable with that setup.
- Which inputs should match my CAM job?
- Match the material, cutting diameter, flute count and spindle RPM to the tool and operation in CAM. Enter the machine's usable cutting feed in inches per minute. The calculator does not read your controller or G-code, so verify the units and machine limits yourself.
- Can I copy the plunge and stepover outputs straight into CAM?
- Check them against the cutter and CAM instructions first. This tool displays plunge at one third of calculated feed and roughing stepover at 40 percent of diameter. Those are fixed estimates; it does not check plunge capability, toolpath engagement, workholding or depth per pass.