Spindle Speed Calculator

Find ideal RPM from cutting speed and tool diameter.

Spindle speed (RPM) 1,145.91

Formula: RPM = SFM × 3.82 ÷ diameter (in)

Step-by-step with your numbers:

1. Values used:

2. Cutting speed = 300 SFM

3. Tool diameter = 1

5. Spindle speed = 1,145.91RPM

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Convert cutting speed into spindle RPM for milling or drilling.

The math behind it

RPM = SFM × 12 ÷ (π × diameter), simplified to RPM = SFM × 3.82 ÷ diameter (in).

300 SFM for 0.5 in tool → ~2,292 RPM.

SFM by material?

Aluminum ~300–600, mild steel ~100–300, stainless ~50–100.