Material Removal Rate Calculator
Material removal rate (MRR) quantifies how much material a CNC machine removes per minute. It is the product of axial depth of cut (how deep), radial width of cut (how wide), and feed rate (how fast). MRR is used to compare machining strategies, estimate cycle times, calculate spindle power requirements, and ensure cut parameters do not overload the machine. The formula below is the standard relationship from Machinery's Handbook.
Material removal rate formula
MRR (in3/min) = DOC (in) * WOC (in) * Feed rate (IPM)
MRR (cm3/min) = MRR (in3/min) * 16.387
Source: Machinery's Handbook (Industrial Press). DOC = depth of cut (axial); WOC = width of cut (radial); IPM = inches per minute.
MRR and spindle power
- Spindle power required is proportional to MRR and the specific cutting energy (kc) of the material.
- Approximate required power (HP) = MRR * kc, where kc is material-specific (aluminum: 0.4 HP/in3/min, mild steel: 1.0 HP/in3/min).
- Add 20 to 30% for spindle efficiency losses when checking against rated spindle power.
- Increasing DOC raises torque demand more than raising feed rate at the same MRR, because chip thickness affects force more than chip rate.
- Start at 50 to 70% of calculated MRR when machining a new material or using a new tool.
Material removal rate calculator: frequently asked questions
What is material removal rate (MRR)?
Material removal rate (MRR) is the volume of workpiece material removed per unit time, measured in cubic inches per minute (in3/min) or cubic millimetres per second (mm3/s). It is used to compare machining efficiency and estimate cycle times.
What is depth of cut (DOC)?
Depth of cut (DOC), also called axial depth of cut, is how deep the end mill engages the workpiece in the axial direction. In a face mill it equals the step-down depth. Typical roughing DOC is 25 to 50% of cutter diameter; finishing DOC can be as low as 0.01 to 0.05 inches.
What is width of cut (WOC)?
Width of cut (WOC), also called radial depth of cut or stepover, is the radial engagement of the cutter in the workpiece. For slotting cuts WOC equals cutter diameter (100% engagement). For peripheral milling, WOC is typically 25 to 50% of cutter diameter.
How is MRR used in practice?
MRR helps select cut parameters that maximise metal removal without overloading the spindle or breaking the cutter. Most spindle manufacturers specify a maximum MRR for their product. Comparing calculated MRR against this limit prevents overload.
How do I convert in3/min to cm3/min?
One cubic inch equals 16.387 cubic centimetres. Multiply in3/min by 16.387 to get cm3/min. Alternatively, multiply mm3/s by 0.06102 to get in3/min.
Official sources
- Industrial Press: Machinery's Handbook (MRR formula and cutting data).
- NIST: Manufacturing Systems Integration Division.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.