CNC Cutting Speed & Feed Rate Calculator
Calculate spindle RPM, feed rate (IPM), chip load, and MRR for any CNC milling operation. SFM auto-fills from material — covers 13 materials.
Free Tool · Instant Results · 13 MaterialsCoated carbide adds ~10–15% SFM. HSS runs ~30–35% of carbide values.
0.25 = 1/4" · 0.5 = 1/2" · 1.0 = 1"
2–3 flutes for aluminum; 4+ flutes for steel and harder materials
Slotting: WOC = tool diameter · Profiling: 25–50% of diameter
| Calculated Output | |
| Spindle Speed | — |
| Feed Rate | — |
| Confirmed SFM | — |
| Chip Load / Tooth | — |
| Cut Efficiency | |
| Material Removal Rate | — |
| DOC × WOC | — |
| Tool Geometry | |
| Tool circumference | — |
| Feed per revolution | — |
SFM & Chip Load Reference — Carbide End Mills
Starting-point values for solid carbide end mills with flood coolant. Coated carbide (TiAlN/AlTiN): add 10–15%. HSS: use 30–35% of these values. Always verify against your tool manufacturer's catalog before production runs.
| Material | SFM (Carbide) | Chip Load 1/4" | Chip Load 1/2" | Chip Load 1" | Key Notes |
|---|---|---|---|---|---|
| Aluminum 6061 / 7075Easy | 600–1,500 | 0.003–0.005" | 0.005–0.008" | 0.008–0.012" | 2–3 flutes; flood coolant prevents chip welding (BUE) |
| Aluminum — CastEasy | 400–900 | 0.002–0.004" | 0.004–0.007" | 0.007–0.010" | Silicon is abrasive; ZrN or DLC coating preferred |
| Mild Steel 1018 / A36Medium | 250–500 | 0.001–0.003" | 0.002–0.005" | 0.004–0.007" | Baseline material; 4 flutes; TiAlN coating recommended |
| Alloy Steel 4140 / 4340Medium | 200–400 | 0.001–0.002" | 0.002–0.004" | 0.003–0.006" | Reduce 20% for prehardened (+30 HRC); AlTiN coating |
| Tool Steel D2 / H13Hard | 100–250 | 0.001–0.0015" | 0.0015–0.003" | 0.002–0.004" | Over 50 HRC: ceramic or CBN tooling required |
| Stainless 304 / 316Hard | 150–350 | 0.001–0.002" | 0.002–0.004" | 0.003–0.005" | Work-hardens — never rub. Keep IPT above 0.001". Flood coolant mandatory |
| Stainless 17-4PHHard | 100–250 | 0.0008–0.0015" | 0.001–0.003" | 0.002–0.004" | Precipitation-hardened; AlTiN / nACRo3 coatings required |
| Brass / BronzeEasy | 400–900 | 0.003–0.005" | 0.004–0.007" | 0.006–0.010" | Free-machining; uncoated carbide fine; watch chip gumming in bronze |
| CopperMedium | 300–600 | 0.002–0.004" | 0.003–0.006" | 0.005–0.008" | Gummy — sharp polished flutes; flood coolant |
| Titanium Ti-6Al-4VHard | 80–200 | 0.0005–0.001" | 0.001–0.003" | 0.002–0.004" | Low thermal conductivity — heat at tool tip. Strict SFM limits |
| Inconel / HastelloyHard | 30–80 | 0.0003–0.0008" | 0.0008–0.0015" | 0.001–0.003" | Highest forces; nACRo3 / AlTiN essential; high-pressure coolant |
| Cast Iron (Gray)Medium | 200–400 | 0.002–0.004" | 0.003–0.006" | 0.005–0.009" | Dry cutting acceptable; abrasive — TiAlN coated tools |
| Plastics (Delrin / Nylon)Easy | 500–1,500 | 0.004–0.007" | 0.006–0.012" | 0.010–0.018" | O-flute or 2-flute; no coolant or light mist |
How CNC Spindle Speed & Feed Rate Are Calculated
Speeds and feeds are the two most fundamental CNC machining parameters. Getting them wrong is the #1 cause of broken tools, poor surface finish, and scrapped parts in U.S. job shops. The formulas are simple — the challenge is knowing the right SFM and chip load for your material/tool combination.
1 SFM to RPM
SFM is a material constant. Since larger tools cover more distance per revolution, RPM must decrease as diameter increases to maintain the same SFM. 3.82 is simply 12 ÷ π.
2 RPM to Feed Rate
Each flute removes one chip per revolution. More flutes = more chips per rev = higher possible feed rate at the same chip load per tooth.
3 Chip Load (IPT)
The thickness each tooth removes per revolution. Too low: rubbing and heat. Too high: breakage. Most critical in stainless and titanium where rubbing causes rapid work hardening.
4 MRR
Material Removal Rate measures machining efficiency. Higher MRR = faster cycle times = lower cost per part. Key metric for comparing toolpath strategies.
Example Calculations — 3 Real-World Scenarios
These worked examples show the calculator in action across three common U.S. shop situations. All use solid carbide end mills with flood coolant and the standard formulas: RPM = (SFM × 3.82) ÷ Ø, Feed = RPM × Flutes × IPT, MRR = Feed × WOC × DOC.
Too light a chip load is worse than too heavy. When chip load is too small, the tool rubs instead of cuts — generating heat, work-hardening the surface (critical in stainless and titanium), causing built-up edge (BUE). If your tool is burning up quickly, try increasing your feed rate before reducing it.