CNC Feed CalculatorRouter Feed Rate & Speed Calculator
Calculate the correct feed rate, surface speed and chip load for CNC routing. Dial in feeds and speeds by material to get clean edges, long tool life and efficient material removal.
Why this calculation matters
Feeds and speeds decide surface quality and tool life. Too slow a feed burns the cut, and burnt hardwood does not sand out to invisible.
CNC Feed Calculator
Router Feed Rate & Speed Calculator
Auto-set by material; fine-tune as needed.
For material removal rate.
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About CNC Feed Calculator
Feeds and speeds determine cut quality, tool life and machining time on a CNC router. The heart of it is chip load - the thickness of material each cutting edge removes per revolution. Get it right and you produce clean edges with long tool life; get it wrong and you either burn and rub (too slow) or chip and snap tools (too fast). This calculator converts spindle speed, flute count and chip load into the exact feed rate to program. It replaces a generic chip load chart for wood with CNC router feeds and speeds computed for your exact cutter and spindle.
Where Is This Used?
Formulas Used
Feed rate (mm/min) = RPM x Number of flutes x Chip loadSurface speed (m/min) = pi x Tool diameter x RPM / 1000Material removal rate = Feed x Depth of cut x Tool dia / 1000Chip load = Feed rate / (RPM x flutes) [to verify]Feed in IPM = Feed mm/min / 25.4 (imperial machines)How the calculation works
Chip load is the thickness each cutting edge removes per revolution, and it is the number that transfers between machines. Feed rate is derived from it, which is why copying a feed rate from another shop rarely works and copying a chip load usually does.
Show the formula
Feed rate = RPM x number of flutes x chip load. Surface speed = pi x tool diameter x RPM / 1000. Material removal rate = feed rate x depth of cut x tool diameter.Chip-load ranges follow the published Onsrud/ShopBot tables, and the recommendation is reduced 25% for a pass twice the tool diameter and 50% for three times, as those tables require. The ranges still span tool diameters, so check your own bit’s data sheet — the manufacturer figure beats a general range every time.
References and what each one provides
- LMT Onsrud / ShopBot feeds and speeds chartsThe industry-standard published chip-load tables by material and tool diameter, with the rule that a bit is rated for a pass depth equal to its cutting diameter and the chip load must be reduced 25% at twice that depth and 50% at three times.Chip-load ranges by material and the published depth-of-cut reduction rule.
Unverified values are marked as such rather than presented as sourced.
Limitations of this calculation
Assumes sharp tooling in sound material at a constant depth of cut. It does not account for tool wear during the run, resin build-up, machine rigidity, vacuum hold-down limits, or grain direction changes within a part.
Do not use this for Production programming without a test cut in the actual material on the actual machine.
Figures are engineering estimates from the inputs and assumptions shown. Verify against the actual material and, where the result affects structure or safety, against a qualified professional.
- Feed rate = RPM × flutes × chip load
Formula checked against the sources above by an automated regression test (tests/test-calculators.js) that derives each expected value independently of this page. Last reviewed .
How to use this tool
- Enter your material and machine details below, then press Calculate.
- Pick your material from the dropdown.
- Fill in tool diameter, number of flutes, spindle speed, chip load per tooth.
- Press Calculate.
Worked example
Common mistakes to avoid
- Slowing down the feed 'to be safe'. Feeding too slow rubs instead of cutting, burns the wood and blunts the tool.
- Using the same chip load for MDF and hardwood. MDF likes bigger chips; hard maple needs smaller ones.
- Running full RPM with a large-diameter cutter. Tip speed climbs with diameter — reduce RPM as the tool gets bigger.
Frequently Asked Questions
Wood species data
Density, hardness and movement for 60 timbers