Drill Speed (RPM) Calculator

How to use this drill speed calculator

Pick your material and enter the bit diameter — the calculator uses a standard cutting speed (surface feet per minute) for that material to recommend an RPM. Bigger bits need slower speeds to hit the same cutting speed at the edge, which is why a 1/8″ bit and a 1/2″ bit in the same material want very different RPMs.

Formula

These SFM values are reasonable starting points for high-speed steel bits under normal shop conditions — cutting fluid, bit quality, and how hard you’re pushing all shift the ideal number. Treat this as a starting RPM to dial in from, not a hard rule.

Reference cutting speeds (SFM)