Speeds and Feeds Calculator

Calculates spindle speed from cutting speed (Vc) and diameter, and the feed rate from feed per tooth or per revolution, for milling, turning, drilling and tapping.

How to use

1. Choose the "Operation" ("Milling", "Turning", "Drilling" or "Tapping") and the "Units" ("Metric" or "Inch").
2. Enter "Cutting speed Vc" and the diameter to get the "Spindle speed". To start from a known speed, set "Start from" to "Spindle speed". A "Machine maximum spindle speed" caps the result.
3. For the feed rate, enter "Feed per tooth fz" and "Number of flutes" (milling), "Feed per revolution f" (turning, drilling) or "Thread pitch" (tapping). Optional sizes add the metal removal rate and time.
4. In "General starting values by material", press "Use" on a row to enter the low end of its range.

How it works

• Spindle speed n = 1000 × Vc ÷ (π × D) with Vc in m/min and D in mm, or n = 12 × SFM ÷ (π × D) with D in inches.
• Milling table feed = fz × flutes × n. Turning and drilling feed = f × n. Tapping feed = pitch × n.
• The material table gives broad ranges from a University of Florida page and a LibreTexts textbook (checked October 2026); carbide is HSS × 2.5. The tool maker's data comes first.
• Values changed with "Edit values" and added materials are saved in this browser.

Questions and answers

How do I calculate milling RPM?

n = 1000 × Vc ÷ (π × D). A 10 mm end mill at 100 m/min turns at about 3,183 rpm.

What is the formula to convert SFM to RPM?

RPM = 12 × SFM ÷ (π × diameter in inches), or roughly 4 × SFM ÷ diameter. At 300 SFM, a 1/2 in cutter turns at about 2,292 rpm.

How do I calculate feed rate in mm/min?

For milling, multiply feed per tooth by flutes and spindle speed. 0.05 mm per tooth, 4 flutes and 3,183 rpm give about 637 mm/min.

What feed rate should I use for tapping?

Exactly pitch × spindle speed. An M8 × 1.25 tap at 300 rpm needs 375 mm/min. Any other feed can break the tap.