Material removal rate (MRR) expresses the volume of work material removed per unit time. For a milling cut with constant rectangular engagement, it is the product of radial width, axial depth, and table feed.
MRR = ae × ap × vf
With millimeter inputs the result is mm³/min; divide by 1,000 for cm³/min. With inch inputs the result is in³/min.
Same MRR, different cuts — worked checks and practical limits.
Milling material removal rate formula
The equation assumes the programmed feed is achieved and the engaged cross-section remains constant. It is especially useful for comparing alternative width/depth/feed combinations or estimating cutting power from a supported material factor.
Metric and inch examples
For 5 mm radial width, 2 mm axial depth, and 800 mm/min feed:
MRR = 5 × 2 × 800 = 8,000 mm³/min = 8.0 cm³/min.
For a 0.200 in radial width, 0.100 in axial depth, and 30 IPM feed:
MRR = 0.200 × 0.100 × 30 = 0.600 in³/min.
| Change | Effect when other inputs stay constant |
|---|---|
| Double radial width | Double MRR |
| Double axial depth | Double MRR |
| Double table feed | Double MRR |
What MRR can and cannot compare
MRR is a productivity measure, not a quality or safety rating. Two cuts can remove the same volume while producing very different tool deflection, chip thickness, heat, torque, surface finish, and chatter risk. Axial-heavy and radial-heavy engagement also load the cutter and workpiece differently.
MRR can be combined with specific cutting energy or specific cutting force to estimate net cutting power. That result remains an estimate because the material factor changes with hardness, chip thickness, tool geometry, rake, wear, coolant, and cutting conditions.
Planning checks
- Use actual engaged width and depth, not nominal tool dimensions.
- Use cutting feed, excluding rapids and non-cutting moves.
- For variable-engagement toolpaths, treat the result as local or average MRR.
- Check spindle power and torque across the intended RPM range.
- Verify chip evacuation, toolmaker limits, holder load, workholding, and machine dynamics.
Same MRR, different engagement: compare two cuts
Consider a nominal 10 mm end mill at the same spindle speed, effective tooth count and 800 mm/min table feed. The two hypothetical rectangular cuts below remove the same volume per minute. They are comparison inputs, not approved machining settings.
| Quantity | A: wide, shallow cut | B: narrow, deeper cut |
|---|---|---|
| Radial width ae | 10 mm (100% of diameter) | 2 mm (20% of diameter) |
| Axial depth ap | 1 mm | 5 mm |
| Feed vf | 800 mm/min | 800 mm/min |
| MRR | 10 × 1 × 800 = 8,000 mm³/min | 2 × 5 × 800 = 8,000 mm³/min |
| Converted MRR | 8.0 cm³/min | 8.0 cm³/min |
Case A engages the full width; case B spreads engagement farther along the cutting edge at a smaller radial immersion. Equal feed and RPM preserve the nominal advance per tooth, but not the instantaneous chip thickness or force history. Case B also requires enough usable cutting-edge length. Tool geometry, entry conditions and chip evacuation determine whether either cut is suitable.
If a simple power model uses the same specific cutting-energy factor, it predicts the same net cutting power for both rows. That assumption does not establish equal peak forces, deflection or chatter risk. Compare the material factor, tool limits and spindle torque at the actual speed before selecting a strategy. Neither row is inherently “safe” or “better” based on MRR alone.
Do not confuse cutting MRR with whole-cycle productivity
In a separate timing example, removing 24 cm³ at a constant 8 cm³/min takes 3 minutes of cutting. Add 2 minutes of non-cutting motion and handling, and the cycle-average removal rate is 24 ÷ 5 = 4.8 cm³/min. Keep the 8 cm³/min local cutting value for the cutting-power estimate; do not use the lower whole-cycle average to size the instantaneous load.
For a changing toolpath, divide it into segments with their own width, depth and achieved feed. Use the MRR and spindle-power calculator to compare those segments, and the chip-thinning guide to examine the separate engagement effect.
Content and numerical examples reviewed October 19, 2026. Examples are not production test results.
Technical references
Published and formula-checked by MfgWorkbench. Last reviewed October 19, 2026. See our editorial method.