CNC / machinist calculator
Material Removal Rate (MRR) Calculator
Material removal rate is the honest measure of how hard a milling cut is working and the number shops use to compare toolpaths and quote jobs. Enter the table feed, the axial depth of cut and the radial width of cut and this calculator returns the MRR in cubic inches per minute and cubic centimetres per minute. It is also the input to the spindle power a cut demands.
How it works
For milling, material removal rate is simply the volume of metal cleared per minute: the table feed in inches per minute times the axial depth of cut times the radial width of cut. The result is in cubic inches per minute, which converts to cubic centimetres per minute by multiplying by about 16.39.
MRR is what actually loads the spindle. Two cuts can share a feed rate yet remove very different volumes if their depth or width differs, and it is the volume, not the feed, that sets the power and torque demand through the material's unit power. That is why a light, fast finishing pass barely touches the spindle while a deep roughing cut at the same RPM can stall it.
Comparing MRR across strategies is how high-efficiency milling proves itself: a light radial width with a deep axial cut and a high feed can clear more volume per minute, with less heat and longer tool life, than a conventional half-width shallow cut. Feed the MRR into the spindle power tool to check your machine can drive it.
Worked example
A 20 in/min feed at 0.1 in deep and 0.25 in wide removes 20 x 0.1 x 0.25 = 0.50 in³/min. In steel at about 1 HP per cubic inch per minute, that is roughly 0.5 HP at the cut.
Frequently asked questions
What is material removal rate?
Material removal rate, or MRR, is the volume of material a cut removes per minute. For milling it is the table feed times the depth of cut times the width of cut, usually reported in cubic inches or cubic centimetres per minute.
How do I calculate MRR for milling?
Multiply the feed rate in inches per minute by the axial depth of cut and the radial width of cut, both in inches. The result is cubic inches per minute; multiply by 16.39 to get cubic centimetres per minute.
Why does MRR matter more than feed rate?
Feed rate alone ignores how deep and wide the cut is. MRR captures the whole volume removed, which is what loads the spindle, so it is the right number for comparing toolpaths and predicting power.
How is MRR related to spindle power?
Required power is the MRR times the material's unit power divided by drive efficiency. Higher MRR needs proportionally more horsepower, so the MRR is the direct input to the can-my-machine-do-this check.
Does high-efficiency milling increase MRR?
It can. A light radial width with a deep axial engagement and a high, chip-thinned feed often clears more volume per minute than a conventional cut, while keeping the cutting edge cooler and lasting longer.
Related calculators
Sources
Every formula on this page is shown and sourced. See how we verify.
These calculators are for planning and as a starting point. Recommended speeds and feeds are published starting values that vary with your specific tool, coating, machine rigidity, workholding and coolant. Always start conservative, listen to the cut, and follow your tool maker data sheet.