What is chip load and why does it matter?

Chip load is the thickness of material removed by each cutting edge per revolution, measured in mm/tooth or inch/tooth. Too low causes rubbing and heat buildup; too high overloads the tool and breaks it. Material presets give a safe starting range — fine-tune by listening for chatter or checking chip color.

What cutting speed should I use?

Cutting speed (surface feet per minute or m/min) depends on the workpiece material and tool coating. Aluminum accepts 200–500 SFM; mild steel 80–150 SFM; stainless steel 30–80 SFM; wood and MDF 500–1500 SFM. The material presets in this calculator use mid-range values as a starting point.

Why does the calculator warn about RPM?

Most hobby and desktop CNC spindles top out at 24,000 RPM. Exceeding the rated speed risks bearing failure and tool ejection. If the calculated RPM is too high, use a larger tool diameter or lower cutting speed.

How do I calculate feed rate from chip load?

Feed Rate (mm/min) = RPM × Number of Flutes × Chip Load (mm/tooth). For example: 18,000 RPM × 2 flutes × 0.05 mm/tooth = 1,800 mm/min.

What is material removal rate (MRR)?

MRR = Feed Rate × Width of Cut × Depth of Cut. It measures cubic mm (or cubic inches) removed per minute and is used to estimate cycle time and spindle load.

CNC Feed Rate Calculator

Name: CNC Feed Rate Calculator
Availability: InStock
Author: Nham Vu

Enter tool diameter, flute count, and material to get recommended RPM and feed rate for CNC machining.

Machining Parameters

Unit System

Material Preset

Tool Diameter (mm)

Number of Flutes

Calculation Mode

Cutting Speed (m/min)

RPM is calculated; chip load sets feed rate.

Chip Load (mm/tooth)

Optional: Material Removal Rate

Width of Cut (mm)

Depth of Cut (mm)

Results

Spindle RPM

—

Feed Rate

—

Chip Load

—

Cutting Speed

—

Formulas used

RPM = (Cutting Speed × 1000) / (π × Diameter) [metric]

RPM = (SFM × 12) / (π × Diameter) [imperial]

Feed Rate = RPM × Flutes × Chip Load

MRR = Feed Rate × Width of Cut × Depth of Cut

Summary

Enter tool diameter, flute count, and material to get recommended RPM and feed rate for CNC machining.

How it works

Select a material preset or enter cutting speed and chip load manually.
Enter the tool diameter and number of flutes.
Choose your unit system (metric or imperial).
The calculator outputs RPM, feed rate, and chip load instantly.
Optionally enter width and depth of cut to see material removal rate.

Use cases

Setting up a hobby CNC router for a new material.
Calculating feed rates for a new end mill or router bit.
Verifying spindle RPM stays within machine limits before cutting.
Estimating material removal rate for cycle time planning.
Cross-checking chip load when troubleshooting tool breakage or chatter.
Converting between imperial and metric cutting parameters.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu