Cutting Speed to RPM and Feed Rate Calculator (m/min and SFM)
Tool catalogs give surface speed, but the machine wants RPM and feed. This calculator converts between them, shows the SFM equivalent of a metric speed and estimates material removal rate for milling.
Your numbers
Surface speed recommended by the tool maker for the material and coating.
Cutter diameter at the cutting edge.
Flutes or inserts on the cutter.
Feed per tooth from the tooling catalog.
Your results
Starting values only. Check the tool maker's recommendations, spindle power and torque, rigidity and chip thinning when ae is less than half the diameter.
Spindle speed (RPM) and feed (mm/min) vs cutting speed
Sweeps Cutting speed Vc from 50 to 400, holding your other inputs fixed.
CNC data into your routings
Want measured cycle times feeding your ERP routings? Ask for an optional expert review.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the cutting speed from the tool maker's chart, the cutter diameter, the tooth count and the chip load per tooth. Add depth and width of cut if you want the removal rate. The result gives spindle RPM, SFM, table feed in mm/min and in/min, and Q in cm3/min. The chart shows how RPM and feed climb with cutting speed, which helps when you test how much a spindle limit or a feed limit constrains the job.
- Cap RPM at the spindle maximum
- Check feed against machine rapid and axis limits
- Reduce Vc for long tool stickout
- Use the radial chip thinning factor for light ae
The formulas
Spindle speed n equals cutting speed times 1,000 divided by pi times diameter, with Vc in m/min and D in mm. In US units RPM is roughly 3.82 times SFM divided by diameter in inches. Table feed equals n times teeth times chip load per tooth. Material removal rate is depth times width times feed divided by 1,000 for cm3/min. One m/min equals 3.28084 SFM. These are the same relations used by CAM systems and tool vendors.
Worked example
A 16 mm four-flute end mill at 200 m/min runs at about 3,979 RPM, which is roughly 656 SFM. With a chip load of 0.05 mm per tooth, feed is about 796 mm/min or 31 in/min. At 10 mm axial and 4 mm radial depth, the removal rate is about 31.8 cm3/min. If the spindle tops out at 3,000 RPM, effective Vc drops to about 151 m/min and feed to about 600 mm/min unless the chip load is raised.
Common mistakes and ERP notes
Typical mistakes are using inches in a metric formula, ignoring chip thinning on light radial cuts, and applying a drilling speed to a milling cutter. In ERP and MES, run times on routings come from feed and cut length, so poor feed assumptions cause standard times to drift from reality. Capturing speed and feed in operation notes or in a tooling database lets planners reuse proven values and gives costing a defensible basis.
- Verify units before entering catalog data
- Store proven feeds with the program revision
- Revisit routing times when feeds change
Frequently Asked Questions
How do I convert SFM to RPM?
RPM is about 3.82 times SFM divided by the tool diameter in inches. For metric, multiply Vc in m/min by 1,000 and divide by pi times diameter in mm. This calculator does the metric version and also shows the SFM equivalent.
What is chip load per tooth?
It is the thickness of material each cutting edge removes per revolution, usually in mm per tooth. Too low causes rubbing and heat, too high causes tool breakage. Use the manufacturer's recommended range for the material and cutter.
How does feed rate relate to cutting time?
Cutting time equals path length divided by feed rate. A higher feed shortens cycle time, so small gains in chip load show up directly in routing run time and in cost per part, within spindle power and rigidity limits.
Does this work for turning and drilling?
The RPM formula applies to any rotating tool or workpiece diameter. The feed and removal rate outputs here are for milling with multiple teeth. For turning use feed per revolution, and for drilling use dedicated drilling formulas.
If routing run times are guesses rather than program data, we can help link CNC cycle times and tooling data to your ERP routings.
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