Engineering Tools

Industrial Unit Converter

Convert between metric and imperial units for machining. Length, cutting speed, and feed rate conversions with high precision.

Industrial Unit Converter

Precision conversions for machining

0.3937

Quick Reference

1 inch =25.4 mm
1 foot =304.8 mm
1/8" =3.175 mm
1/4" =6.35 mm

High-precision conversions • 6 decimal places available

Click result to copy

Essential Conversions for Machinists

Length Conversions

  • 1 inch = 25.4 mm
  • 1 foot = 304.8 mm
  • 1 thou (mil) = 0.0254 mm
  • 1 mm = 0.03937 inches

Speed Conversions

  • 1 SFM = 0.3048 m/min
  • 100 SFM = 30.48 m/min
  • 1 m/min = 3.281 SFM
  • 1 mm/s = 0.06 m/min

What is SFM (Surface Feet per Minute)?

SFM is the imperial unit for cutting speed — the speed at which the cutting edge travels across the workpiece surface. It's essential for determining the correct RPM for a given tool diameter. The metric equivalent is m/min (meters per minute).

RPM Formula with SFM

RPM = (SFM × 3.82) / Diameter (inches)

For metric: RPM = (Vc × 1000) / (π × D mm)

Feed Rate: IPR vs mm/rev

Feed rate determines how much material the tool advances per revolution. IPR (inches per revolution) is common in the USA, while mm/rev is the global metric standard. For milling, feed is often expressed per tooth (IPT or mm/tooth).