[BUG] In inch mode (G20), Move menu shows unit "mm" on the display

[DerAndere1]

Did you test the latest bugfix-2.1.x code?

Not yet

Bug Description

[BUG] In inch mode (G20), the display move menu shows unit "mm" instead of "in". The values in the menu are representing move distance in inches, but the unit is shown as "mm".

Bug Timeline

Max 3 years. probably since commit 36e66bd

Expected behavior

[BUG] In inch mode (G20), MarlinUI Move menu should show unit "in".

Actual behavior

[BUG] In inch mode (G20), MarlinUI Move menu should show unit "mm".

Steps to Reproduce

1. Send G20 to enable inch mode
2. On the display in "Marlin mode" (using MarlinUI), go to Move Menu and select one of the XYZ axes
3. Observe that distance values are in inches but their unit is labeled as "mm"
4. Select the entry "Move 0,1 mm
5. Observe that the axis moves 0,1 inch

Version of Marlin Firmware

Custon, based on bugfix-2.1.x from 14th March 2026 (commit 6999985)

Printer model

Custom

Electronics

BTT_GTR V1.0

LCD/Controller

BTT touch dislay, works with REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER (touch mode and Marlin mode affected)

Other add-ons

No response

Bed Leveling

None

Your Slicer

None

Host Software

SD Card (headless)

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

Not sure but my first guess is that this regression was introduced in commit 36e66bd

Config an source code:
https://github.com/DerAndere1/Marlin2ForPipetBot/tree/Marlin2ForPipetBot/config/examples/DerAndere/HendrikJan5D_HH

[ellensp]

In Marlin/src/lcd/menu/menu_motion.cpp is

  else if (parser.using_inch_units()) {
    #ifdef MANUAL_MOVE_DISTANCE_IN
      #define _MOVE_IN(I) __MOVE_SUB(MSG_MOVE_N_MM, STRINGIFY(I), IN_TO_MM(I));
      MAP(_MOVE_IN, MANUAL_MOVE_DISTANCE_IN)
    #endif
  }

but MSG_MOVE_N_MM is wrong, it should be MSG_MOVE_N_IN

ie it should be

  else if (parser.using_inch_units()) {
    #ifdef MANUAL_MOVE_DISTANCE_IN
      #define _MOVE_IN(I) __MOVE_SUB(MSG_MOVE_N_IN, STRINGIFY(I), IN_TO_MM(I));
      MAP(_MOVE_IN, MANUAL_MOVE_DISTANCE_IN)
    #endif
  }

Was added in error in #26438

[DerAndere1]

Yes, I found the same mistake. MarlinUI will be fixed with pr #28363 . BTT display in touchmode: I dont plan to fix that.