# LinuxCNC G91.1

Instructions · `G91.1` · verification: source checked

G91.1 is the LinuxCNC G-code that selects incremental arc distance mode for the I, J and K offsets used with G2 and G3 arc moves. In this mode the arc centre offsets are distances relative to the start location of the arc. G91.1 returns I, J and K to their default behaviour, which is incremental arc distance mode.

## Specification

| Property | Value |
|---|---|
| Language | gcode |
| Code | G91.1 |
| Group | Arc Distance Mode |
| Dialect | LinuxCNC |

## Connected

- Related: [LinuxCNC G02](https://machineschema.com/instruction/gcode-g02.md)

## Study notes

- Incremental arc distance mode is the default mode for arc centre offsets.
- In incremental arc distance mode, arc centre offsets are a relative distance from the start location of the arc.
- The arc centre is treated as absolute or relative as set by G90.1 or G91.1 respectively.
- In absolute arc distance mode (G90.1), both I and J must be given for arcs in the XY plane, or J and K for the XZ plane, otherwise it is an error.

## Sources

1. [G-Codes](https://linuxcnc.org/docs/html/gcode/g-code.html#gcode:g90.1-g91.1) (accessed 2026-10-26)

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Source page: https://machineschema.com/instruction/gcode-g91-1  
JSON: https://machineschema.com/instruction/gcode-g91-1.json  
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite Machine Schema and the original sources.