CNC Material Removal Rate Calculator
Material removal rate (MRR) tells you how much material your CNC mill cuts away per minute. It is the product of the radial width of cut, the axial depth of cut, and the linear feed rate. MRR is the headline productivity number in milling: higher values machine parts faster but demand more spindle power and accelerate tool wear. Enter width, depth, and feed in matching units and this calculator returns MRR in the matching volume-per-minute unit.
Material removal rate formula
MRR = width of cut * depth of cut * feed rate
Keep all three inputs in the same length unit. Inches with inches per minute give cubic inches per minute; millimetres with mm per minute give cubic millimetres per minute.
Worked example
A cut with width 0.25 in, depth 0.1 in, and feed 20 in/min gives MRR = 0.25 * 0.1 * 20 = 0.50 cubic inches per minute. Doubling the depth to 0.2 in doubles MRR to 1.00, but also roughly doubles cutting force, so confirm the spindle and tool can handle it.
Material removal rate: frequently asked questions
What is material removal rate?
Material removal rate, or MRR, is the volume of material a cutting tool removes per unit time. For milling it equals the width of cut multiplied by the depth of cut multiplied by the feed rate. It is a direct measure of machining productivity and a useful figure for comparing toolpaths and estimating cycle time and spindle load.
What units does this calculator use?
It uses consistent units that you choose. If width and depth are in inches and feed rate is in inches per minute, MRR comes out in cubic inches per minute. If you work in millimetres and mm per minute, MRR is in cubic millimetres per minute. The formula is the same; just keep all three inputs in the same length unit.
Why does MRR matter?
A higher MRR means faster machining but more spindle power and heat, more tool wear, and higher cutting forces. Comparing the MRR of different cut strategies helps you balance speed against tool life and surface finish. Machine and tool makers publish maximum recommended MRR for given materials and tools.
Does MRR include the cutting speed or RPM?
Not directly. MRR depends on the engaged cross-section (width times depth) and how fast the tool advances (feed rate). Spindle RPM and chip load determine the feed rate you can use safely, so they affect MRR indirectly through the feed you enter.
Sources and method
- MRR is the standard milling productivity formula: engaged cross-section times feed rate. It is a geometric identity, not a sourced figure.
- National Institute of Standards and Technology: Manufacturing and machining research.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.