G29 - Bed Leveling (Linear)

calibration Probe the bed and enable leveling compensation. AUTO_BED_LEVELING_LINEAR


Automatic (Linear) Bed Leveling probes the bed in a grid and enables bed leveling compensation using a matrix to compensate for bed tilt, applying a “least-squares” approximation.

The printer must be homed with G28 before G29.

Automatic Probing

Using an electronic probe Marlin can probe the entire grid with a single G29 command. See parameter descriptions and examples below for details.

Manual Probing

Click for Details

Auto Bed Leveling now includes a PROBE_MANUALLY option for systems lacking a probe.

PROBE_MANUALLY adds these parameters to G29:

  • Q : Query leveling and G29 state
  • A : Abort current leveling procedure

To do manual probing simply repeat G29 until the procedure is complete.

The first G29 accepts the same parameters , shown in the Usage section below. The exact parameters available will depend on which style of bed leveling is enabled. (Note: UBL parameters are not covered on this page unless they coincide. See the G29 for UBL page for a full list of its options.)

Before probing the bed:

  1. Use G29 Q to get the current status. If G29 isn’t idle, abort with G29 A.
  2. Use M420 V to view leveling data. You can send M420 S1 to use the existing data.

To probe the bed using G-code:

  1. Use G29 to move to the first point for Z adjustment.
  2. Adjust Z so a piece of paper can just pass under the nozzle.
  3. Use G29 to save the Z value and move to the next point.
  4. Repeat steps 3-4 until completed.
  5. Use M500 to save the leveling data to EEPROM, if desired.

To probe the bed using your LCD controller: (Requires LCD_BED_LEVELING)

  1. Select the Level Bed sub-menu, then choose Level Bed (not Cancel).
  2. Wait for Homing XYZ to complete.
  3. When Click to Begin appears, press the controller button to move to the first point.
  4. Use the controller wheel to adjust Z so that a piece of paper can just pass under the nozzle.
  5. Press the controller button to save the Z value and move to the next point.
  6. Repeat steps 4-5 until completed.
  7. Use Control > Store memory to save the mesh to EEPROM, if desired.


Any arguments left out of G29 will use the default values set in Configuration.h.

G28 disables bed leveling. Follow with M420 S to turn leveling on, or use RESTORE_LEVELING_AFTER_G28 to automatically keep leveling on after G28.

To save time and machine wear, save your matrix to EEPROM with M500 and in your slicer’s “Starting G-code” replace G29 with M420 S1 to enable your last-saved matrix.


G29 [A<bool>] [B<linear>] [C<bool>] [D<bool>] [E<bool>] [F<linear>] [H<linear>] [J<bool>] [L<linear>] [O] [P<int>] [Q<bool>] [R<linear>] [S<rate>] [T<bool>] [V<0-4>] [X<int>] [Y<int>]



Abort leveling procedure in-progress (PROBE_MANUALLY)


Set the back limit of the probing grid.


Create a fake grid for testing. (DEBUG_LEVELING_FEATURE)


Dry-Run mode. Just probe the grid but don’t update the bed leveling data

  • By default G29 will engage the Z probe, test the bed, then disengage.
  • Include “E” to engage/disengage the Z probe for each sample.
  • There’s no extra effect if you have a fixed Z probe. (without PROBE_MANUALLY)

Set the front limit of the probing grid.


Set the square width and height of the area to probe.


Jettison the leveling data stored in SRAM and turn off leveling compensation. Data in EEPROM is not affected.


Set the left limit of the probing grid.


Optional. If leveling is already enabled then exit without leveling. (1.1.9)


Set the size of the square grid that will be probed - P x P points


Query the current leveling state (PROBE_MANUALLY, DEBUG_LEVELING_FEATURE)


Set the right limit of the probing grid.


Set the XY travel speed between probe points.


Generate a Bed Topology Report


Set the verbose level. Level 2 and up act like ‘T’.


Set the number of columns (in X) that will be probed.


Set the number of rows (in Y) that will be probed.