This free CNC speeds and feeds calculator gives you the spindle speed (RPM) and feed rate for milling with an end mill, on a CNC mill or a CNC router. Pick the workpiece material and enter the tool diameter and number of flutes. Add the width and depth of cut to get the metal removal rate and to correct the feed for chip thinning on light cuts. It uses the classic shop formulas and works in inch or metric units.
Milling Speeds and Feeds Calculator
Milling Speeds and Feeds Calculator
For HSS end mills (carbide can usually run 2–3× the surface speed; check the tool maker's numbers). Picking a material fills in the surface speed and a chip load from the tables below, scaled by tool size (the low end of the range for 1/8" tools and under, rising to the high end at 1"). Edit either value to override it. RPM = SFM × 12 ÷ (π × diameter); feed rate = RPM × flutes × chip load. When the width of cut is less than half the diameter, the feed is raised to keep the same chip thickness.
What is SFM, and how do you go from SFM to RPM?
Milling Surface Speeds and Chip Loads for HSS End Mills
These are the starting values the calculator uses.
| Workpiece Material | Surface Speed (SFM) | Chip Load (IPT) |
|---|---|---|
| Aluminum - Wrought (6061) | 250 | 0.005 - 0.010 |
| Brass | 200 | 0.005 - 0.010 |
| Cast Iron - Ductile | 90 | 0.004 - 0.008 |
| Cast Iron - Gray | 100 | 0.002 - 0.006 |
| Copper Alloy - Wrought | 120 | 0.004 - 0.008 |
| Magnesium Alloy | 250 | 0.005 - 0.010 |
| Stainless Steel | 30 | 0.002 - 0.006 |
| Steel - Mild | 110 | 0.002 - 0.010 |
| Steel - Hard Alloy | 60 | 0.002 - 0.006 |
| Steel - Tool | 60 | 0.002 - 0.006 |
| Wood - Hardwood | 500 | see the wood chart |
Chip load should be adjusted for tool diameter: smaller tools need much lower chip loads, so use the low end of the range for small end mills. You can also look it up in the tool maker's catalog. For wood, see our CNC Feeds and Speeds Chart for Wood. For twist drills, use our Drilling Speeds and Feeds Calculator, and for taps, our Tap Speed and Feed Calculator.
How to Calculate Material Removal Rate?
Generally, you want to find the highest Material Removal Rate that will keep reasonable tool life. The calculator above shows the removal rate for your width and depth of cut. You may want to click through this article to find the Material Removal Rate Formula.
How to Calculate Feed Rate?
Wondering how to calculate feed rate? Perhaps so you can create your own spreadsheet?
The basic feed rate formulas for milling are simple, but getting real-world feeds and speeds are quite a bit harder. We give you all the basic formulas in our free online Feeds and Speeds Course. It's easier just to use one of our two Cnc Milling Speeds And Feeds Calculators.
More Feeds and Speeds Calculators
- Milling Speeds and Feeds Calculator
- CNC Router Feeds and Speeds Calculator
- Lathe Feeds and Speeds Calculator
- Drilling Speeds and Feeds Calculator
- Tap Speed and Feed Calculator
- Chip Load Calculator
- SFM to RPM Calculator
- All free CNC calculators
Be the first to know about updates at CNC Cookbook
Join our newsletter to get updates on what's next at CNC Cookbook.