CNC Feeds and Speeds Calculator
A CNC feeds and speeds calculator turns the cutting speed for a material into the two numbers a CNC control actually needs: spindle RPM and feed rate. This tool handles both a CNC milling center (VMC) cutting metals and a CNC router feeds and speeds calculator scenario with hardwood, MDF, plywood, plastic, and foam. Every output matches the same SFM and chip load equations a Fusion 360, Mastercam, or Vectric toolpath uses.
CNC feeds and speeds equations
- Spindle RPM = (SFM x 12) / (pi x D) where SFM is surface feet per minute and D is cutter diameter in inches.
- Feed rate (IPM) = RPM x chip load x flutes.
- Metric feed rate = IPM x 25.4 mm/min.
Example (metal, VMC): 1/4 inch 2-flute carbide end mill in 6061 aluminum at 1500 SFM, 0.003 IPT scaled by tool diameter. RPM = (1500 x 12) / (pi x 0.25) = 22,918 RPM. Feed = 22,918 x 0.003 x 2 = 137.5 IPM = 3,492 mm/min. If your machine tops out at 12,000 RPM, cap RPM and recompute feed: 12,000 x 0.003 x 2 = 72 IPM.
Example (wood, router): 1/4 inch 2-flute router bit in hardwood at 2200 SFM, 0.008 IPT baseline. RPM = (2200 x 12) / (pi x 0.25) = 33,614 RPM (most routers spin 10,000 to 24,000 RPM, so cap at machine max). At 18,000 RPM and 0.008 IPT with 2 flutes: feed = 18,000 x 0.008 x 2 = 288 IPM = 24 ft/min. That is a realistic CNC router feeds and speeds calculator result for a 1/4 inch bit in hardwood.
CNC feeds and speeds chart
| Material | Carbide SFM | Chip load (IPT) |
|---|---|---|
| Aluminum 6061 | 1500 | 0.004 |
| Mild steel (1018) | 400 | 0.002 |
| Alloy steel (4140) | 280 | 0.0015 |
| Stainless 304/316 | 220 | 0.0015 |
| Titanium Ti-6Al-4V | 120 | 0.001 |
| MDF | 2500 | 0.010 |
| Hardwood (oak, maple) | 2200 | 0.008 |
| Softwood (pine) | 2800 | 0.012 |
| Plywood | 2300 | 0.009 |
| Plastic (Delrin, acrylic) | 2000 | 0.005 |
| Foam (polyurethane) | 3000 | 0.015 |
A printable CNC feeds and speeds chart pdf built from these values works as a shop-wall reference. The numbers here are the same values that go into Harvey Tool, Helical, and Onsrud starting-point tables.
CNC router feeds and speeds calculator notes
A CNC router spins 10,000 to 24,000 RPM (Makita RT0701, Porter-Cable 892, Bosch 1617) with 1/4 inch collet. The RPM the metals formula gives for small bits in wood usually exceeds router max, so cap at the machine max and accept a slightly lower SFM. In softwood and foam, chip load is the feed-rate bottleneck, so you can often bump IPT to get feed up without overloading the bit. A CNC feeds and speeds calculator wood entry should return feed in hundreds of IPM, not single digits.
CNC feeds and speeds calculator app vs starting point
Production shops run purpose-built CNC feeds and speeds calculator app subscriptions (Productive, G-Wizard, HSMAdvisor) that tune for your specific tool, toolholder, stickout, and machine rigidity. This online calculator gives the same starting-point numbers those apps do before any tuning; dial feed up or down 20 percent based on chip color, spindle load, and sound.
Chip load scaling by tool diameter
Small cutters cannot take full IPT because the flute has less room for the chip. This calculator scales chip load down to 50 percent for bits under 1/8 inch, 75 percent for bits 1/8 to 1/4 inch, and up to 125 percent for bits over 3/4 inch. A CNC feeds and speeds calculator that does not scale chip load for bit size will undercut tool life on small tools.