G20 and G21 : Inches and Metric

Overview

These G-Codes specify the dimension unit for the input data between "inches" (G20) and “mm” (G21) used for positioning commands.

Command Format

• Syntax: G20 or G21

Examples

Note G21 // set program to millimeters G01 X25.4 F1000``` - The G-code above will move to **25.4 mm** at **1000mm/min**

Details

• The default value at startup is G21
• G20 - Inch Mode
• Feed (G1, G2, G3) and Rapid (G0) moves are interpreted in inches
• Feed Rates are inches per minute

• G21 - Metric Mode
• Feed (G1, G2, G3) and Rapid (G0) moves are interpreted in millimeters after this command
• Feed Rates are mm per minute
• Best Practices
• Always keep this command on its own line
• Always specify at the top of the program or when in doubt of what the current active units are

See Also:

• G-Code Command Priority
G-Code Command Priority