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Feed Formula

Milling Feed Rate Formula

Convert spindle speed, flute count, and chip load into programmed table feed for CNC milling.

Direct answer: feed rate = RPM x flutes x chip load. Use inches for IPM and millimeters for mm/min, then validate against toolmaker chip-load ranges and machine load.

Feed Rate Formula

Feed Rate = RPM x Number of Flutes x Chip Load

Chip load is feed per tooth. Do not substitute total feed rate into the chip-load field.

Imperial Example

A 3-flute end mill runs at 6,000 RPM with a target chip load of 0.003 inches per tooth.

Feed Rate = 6,000 x 3 x 0.003 = 54 IPM

Metric Example

A 4-flute cutter runs at 8,000 RPM with a target chip load of 0.05 mm/tooth.

Feed Rate = 8,000 x 4 x 0.05 = 1,600 mm/min

When to Use the Full Calculator

This page explains the formula. Use the feeds and speeds calculator when you also need material selection, SFM, depth of cut, MRR, and power context in one workflow.