Drilling RPM calculator
Pick the material, enter the drill diameter, and get the spindle speed — with the cutting speed and rpm editable in both directions if your machine or drill needs something different.
How drill speed is calculated
Every material has a preferred cutting speed (Vc, in metres per minute) — how fast the drill's cutting edge should travel through it. The spindle speed follows from the drill diameter: n = (Vc × 1000) / (π × Ø). That's why a 3 mm drill spins much faster than a 20 mm drill in the same material: the small drill's edge covers far less distance per revolution.
Which tooling do the default speeds assume?
Standard HSS (high-speed steel) drills — deliberately conservative starting values. Cobalt or carbide drills, good cooling and rigid setups allow higher speeds: edit the Vc field and the rpm updates instantly.
Why does stainless steel run so slow?
Stainless work-hardens: if the drill rubs instead of cuts, the surface gets harder and the drill dulls fast. A low speed with steady feed pressure keeps the edge cutting under the hardened layer.
Are these values safe to use directly?
They are common starting values, not guarantees. Always respect your machine's limits and your tool manufacturer's data sheet, reduce speed for deep holes or poor cooling, and wear eye protection.
Is my data sent anywhere?
No — this runs entirely in your browser with plain JavaScript. Nothing is uploaded.
