The feed rate is how fast the work moves past a milling cutter, and it's built up tooth by tooth: Vf = N × fz × z. Each tooth takes a bite of size fz (the feed per tooth or chip load), there are z teeth, and the spindle turns N times a minute — multiply them for the table feed in mm/min. It pairs with cutting speed: the surface speed and diameter set the RPM, and that RPM drives the feed rate. Dialling in the right chip load is what keeps the cut clean and the tool alive.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: the milling feed-rate relation Vf = N·fz·z.
The feed rate equations
The feed per tooth is the basic per-edge advance set by the tool maker; multiplying by the tooth count gives the feed per revolution, and multiplying again by the RPM gives the table feed per minute. To work backwards — say, to hit a target feed rate — divide it by the product of the other two known quantities. The imperial form is identical with inches per tooth (IPT) and inches per minute (IPM).
Worked example — a 4-flute end mill
Scenario: A 4-flute end mill runs at 637 RPM (set by the cutting speed) with a recommended feed per tooth of 0.1 mm. What feed rate do you program?
Program about 255 mm/min, which is 0.4 mm of advance per revolution. Drop the chip load to 0.05 mm and the feed halves to ~127 mm/min; push it to 0.15 mm and it climbs to ~382. A 2-flute cutter at the same RPM and chip load would feed at half the rate of the 4-flute, because fewer teeth take fewer bites per turn — which is why flute count matters as much as the per-tooth figure.
Frequently Asked Questions
Vf = N × fz × z. 637 RPM × 0.1 mm × 4 flutes = 254.8 mm/min. Imperial: IPM = RPM × IPT × teeth.
The advance per cutting tooth — the chip thickness each tooth removes, set by the tool maker.
Feed rate is mm/min; feed per rev is fz×z (mm per turn). Feed rate = feed/rev × RPM.
Cutting speed + diameter set the RPM; that RPM feeds Vf = N·fz·z. Find RPM first, then feed.
N = Vf/(fz×z). 254.8 ÷ (0.1×4) = 637 RPM. Leave RPM blank and the calc solves it.