Cutting Speed Calculator

How to calculate spindle speed from cutting speed

1. Choose metric or imperial units, and whether to calculate the spindle speed or the cutting speed.
2. Enter the diameter of the cutter, drill or workpiece, and the cutting speed or RPM.
3. Add the feed per tooth and the number of teeth or flutes to get the feed rate.

Frequently asked questions

What is the formula?

RPM = cutting speed × 1000 ÷ (π × diameter in mm) for m/min, or SFM × 12 ÷ (π × diameter in inches). For milling and drilling the diameter is the tool's; for turning it is the workpiece's.

Where do I find the cutting speed?

From the tool maker's data for your tool and material. As a rough guide with carbide tools: around 100 to 250 m/min for steel and 300 m/min or more for aluminium; high-speed steel tools run at roughly a quarter to a third of that.

How is the feed rate worked out?

Feed rate = RPM × feed per tooth × number of teeth. For a drill or a lathe, enter the feed per revolution and 1 tooth.