CNC Feed and Speed Calculator

When to use this manufacturing calculator

• Use it before comparing a starter feed and speed against tooling supplier charts.
• Use it when converting between surface speed, RPM, feed per tooth, feed per revolution, and feed rate.
• Use it for preliminary CNC setup notes before CAM programming or shop review.

How to use

1. Enter the manufacturing dimensions, speeds, feeds, process values, and material assumptions for one preliminary calculation.
2. Click the exact calculator action button; default values, typing, URL-prefilled values, and worked examples do not generate results automatically.
3. Review warnings, assumptions, result visual, copy text, and downloads before using output in a shop, drawing, supplier, or process-planning workflow.
4. Verify every final value against machine documentation, tooling supplier guidance, material data, inspection requirements, and qualified manufacturing review.

Input guide

Unit system

Metric uses diameter in mm and cutting speed in m/min; inch uses diameter in inches and cutting speed in SFM.

Tool diameter and cutting speed

Used to calculate RPM when cutting speed is supplied.

Feed per tooth, teeth, feed per revolution, and feed rate

Used according to the selected calculation mode.

Notation

Output interpretation

• Spindle speed, cutting speed, feed rate, feed per tooth, warnings, visual summary, and CSV/Markdown downloads.

Supported manufacturing use cases

• starter CNC milling feeds and speeds
• turning feed-rate checks
• chip-load reverse checks
• metric and inch planning values

Unsupported patterns

• toolpath generation
• adaptive clearing strategy selection
• machine post processing
• vendor-specific tool grade selection

How to interpret the output

• Higher RPM and feed can exceed machine, toolholder, or workholding limits.
• Chip load must be verified against tool diameter, flute count, material, rigidity, and coolant.

Manufacturing planning guidance

• Use supplier charts and machine limits after calculating the relationship.
• Reduce values cautiously for poor rigidity, long stickout, or interrupted cuts.

Worked examples

Assumptions

• Inputs are user-entered planning values and are not extracted from CAD files, CNC code, CAM systems, drawings, or shop databases.
• Metric calculations use millimetres, metres per minute, millimetres per minute, and SI-derived output where stated.
• Inch calculations use inches, surface feet per minute, inches per minute, and inch-derived output where stated.
• Tool diameter is the effective cutting diameter.
• Tooth count is engaged consistently for a simple planning estimate.

Practical guidance

• Pair with MRR and machining time after selecting a feed relationship.

Common mistakes

• Using inch SFM in the metric RPM formula.
• Forgetting flute count in feed-rate calculations.
• Treating calculated values as supplier-approved parameters.

Limitations

• No correction is made for radial chip thinning, tool wear, runout, interrupted cuts, or machine acceleration.
• ScholarTool manufacturing calculators provide general engineering calculation and planning support. They do not replace supplier requirements, tooling recommendations, machine-tool documentation, process qualification, inspection standards, or professional manufacturing review.
• The tool does not select a tool grade, coating, holder, fixture, coolant strategy, inspection plan, or supplier-approved process.
• The tool does not generate or execute G-code, CAM toolpaths, CNC simulations, machine programs, or production schedules.

Related workflow links