# CNC Feeds and Speeds Calculator

CNC feeds and speeds calculator for VMCs and CNC routers. Returns spindle RPM, feed rate (IPM and mm/min), chip load, and SFM for metals, hardwood, MDF, plywood, plastic, and foam.

## What this calculates

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.

## Inputs

- **Machine Type** — options: CNC mill / VMC, CNC router (wood, foam, plastic) — CNC router feeds and speeds calculator uses the wood/foam chip load table; CNC mill uses the metals table.
- **Cutter Diameter** (in) — min 0.001 — Cutter (end mill, router bit, compression bit) diameter.
- **Material** — options: Aluminum (metal), Mild steel / 1018 (metal), Alloy steel / 4140 (metal), Stainless steel (metal), Cast iron (metal), Brass (metal), Titanium (metal), MDF (router), Hardwood (router), Softwood (router), Plywood (router), Plastic / acrylic, Foam / polyurethane — Pick the workpiece material. Wood/foam options are for CNC router use.
- **Cutter Material** — options: HSS, Carbide — Carbide is standard on CNC mills and modern routers.
- **Flutes** — min 1, max 8 — 2 for aluminum or router, 3-4 for steel, 1-2 for softwood/foam.
- **Chip Load Override** (in/tooth) — min 0 — Optional. Enter a specific chip load per tooth from a vendor data sheet.

## Outputs

- **Spindle RPM** (RPM) — RPM = (SFM x 12) / (pi x D).
- **Cutting Speed** (SFM) — Surface feet per minute for the material + tool combo.
- **Feed Rate** (IPM) — Feed rate = RPM x chip load x flutes.
- **Feed Rate (metric)** (mm/min) — Feed rate in mm/min for metric CNCs.
- **Chip Load** (IPT) — Chip load per tooth used in the feed equation.
- **Note** — formatted as text — Usage note for the machine type and material.

## Details

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

  
    MaterialCarbide SFMChip load (IPT)
  
  
    Aluminum 606115000.004
    Mild steel (1018)4000.002
    Alloy steel (4140)2800.0015
    Stainless 304/3162200.0015
    Titanium Ti-6Al-4V1200.001
    MDF25000.010
    Hardwood (oak, maple)22000.008
    Softwood (pine)28000.012
    Plywood23000.009
    Plastic (Delrin, acrylic)20000.005
    Foam (polyurethane)30000.015
  

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.

## Frequently Asked Questions

**Q: How do I calculate CNC feeds and speeds?**

A: Two equations. RPM = (SFM x 12) / (pi x D) turns a target surface speed into spindle RPM. Feed rate (IPM) = RPM x chip load x flutes turns RPM into linear feed. This CNC feeds and speeds calculator does both steps and returns the feed in both IPM and mm/min.

**Q: Can I use a CNC router feeds and speeds calculator for metals?**

A: You can for aluminum with a rigid setup, a compression bit, and mist coolant. Most CNC routers are not rigid enough for steel or stainless. If you need steel on a router, stay at 1/8 inch bits, under 0.050 depth per pass, and accept slow feed. For a true metal CNC feeds and speeds calculator workflow, use a VMC.

**Q: What is a good CNC feeds and speeds chart for wood?**

A: Hardwood 2200 SFM carbide at 0.008 IPT, softwood 2800 SFM at 0.012 IPT, plywood 2300 SFM at 0.009 IPT, MDF 2500 SFM at 0.010 IPT. A full CNC feeds and speeds chart wood version is baked into this calculator. Print the result as your shop's CNC feeds and speeds chart pdf reference.

**Q: Is there a CNC feeds and speeds calculator app?**

A: Yes, multiple. G-Wizard (subscription), HSMAdvisor (subscription), FSWizard (free tier). Each tunes for toolholder and machine rigidity on top of the basic SFM and chip load equations. This free online CNC feeds and speeds calculator app-style tool returns the same starting-point numbers without the tuning overhead.

**Q: Does CNC feeds and speeds calculator wood mode produce higher RPM than metal mode?**

A: Yes, often 5-10x higher. Wood SFM is 1200-3000 vs steel at 200-400. For the same 1/4 inch bit, that is 18,000-45,000 RPM in wood vs 3,000-6,000 RPM in steel. Wood-only CNC routers spin 18,000-24,000 RPM, which caps the high end; VMCs go to 12,000-24,000 RPM and handle both.

**Q: Why does chip load per tooth vary so much between woods and metals?**

A: Wood and foam chip off easily and have low cutting force, so you can take a thick chip per tooth. Metals have high cutting force and require a thinner chip to keep tool temperature down. A CNC feeds and speeds chart in the Sandvik, Harvey Tool, and Onsrud data books reflects exactly this: wood IPT 0.008-0.015, steel IPT 0.001-0.003.

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Source: https://vastcalc.com/calculators/physics/cnc-feeds-and-speeds
Category: Physics
Last updated: 2026-04-08