Material removal rate (MRR) is one of the simplest ways to approximate the spindle power required for a milling operation.
For milling, the basic formula is:
MRR = width of cut × depth of cut × feed rate
Example: 10 mm width × 2 mm depth × 1500 mm/min feed = 30,000 mm³/min
Try it yourself using the MRR Calculator.
A common approximation is:
Power (kW) ≈ (MRR × Kc) / (60 × 1000)
where Kc is the specific cutting force of the material. Typical values include:
Use the Spindle Power Estimator to calculate both MRR and power in one step.
If your machine spindle has a rated power (for example 15 kW), you can estimate spindle load percentage:
load % = (required power / rated power) × 100
Use this as a guideline only—actual power depends on tool geometry, chip thinning, engagement angle, tool wear and machine efficiency.