---
tag: g029g2
title: Bed Leveling (Linear)
brief: Probe the bed and enable leveling compensation.
author: thinkyhead

group: calibration
requires: AUTO_BED_LEVELING_LINEAR
eeprom: true

codes: [ G29 ]
related: [ M420 ]

notes: |
  - Any arguments left out of `G29` will use the default values set in `Configuration.h`.
  - By default `G28` disables bed leveling. Follow `G28` with `M420 S` to turn leveling on.
      - With `ENABLE_LEVELING_AFTER_G28` leveling will always be enabled after `G28`.
      - With `RESTORE_LEVELING_AFTER_G28` leveling is restored to whatever state it was in before `G28`.
  - To save time and machine wear, save your matrix to [EEPROM](/docs/features/eeprom.html) with [`M500`](/docs/gcode/M500.html) and in your slicer's "Starting G-code" replace `G29` with `M420 S1` to enable your last-saved matrix.
  - For multi-axis machines (`I_DRIVER_TYPE` defined) without implementation of inverse kinematics, bed leveling produces wrong results while the toolhead is not oriented vertical and perpendicular to the bed and must be turned off with `M420 S0`

parameters:

- tag: A
  optional: true
  description: Abort leveling procedure in-progress (`PROBE_MANUALLY`)
  values:
  - type: bool

- tag: C
  optional: true
  description: Create a fake grid for testing. (`DEBUG_LEVELING_FEATURE`)
  values:
  - type: bool

- tag: O
  type: bool
  optional: true
  description: Optional. If leveling is already enabled then exit without leveling. (1.1.9)

- tag: Q
  optional: true
  description: Query the current leveling state (`PROBE_MANUALLY`, `DEBUG_LEVELING_FEATURE`)
  values:
  - type: bool

- tag: X
  optional: true
  description: Set the number of columns (in X) that will be probed.
  values:
  - type: int

- tag: Y
  optional: true
  description: Set the number of rows (in Y) that will be probed.
  values:
  - type: int

- tag: P
  optional: true
  description: Set the size of the square grid that will be probed - P x P points
  values:
  - type: int

- tag: S
  optional: true
  description: Set the XY travel speed between probe points.
  values:
  - tag: rate
    type: float

- tag: E
  optional: true
  description: |
    - 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`)
  values:
  - type: bool

- tag: D
  optional: true
  description: Dry-Run mode. Just probe the grid but don't update the bed leveling data
  values:
  - type: bool

- tag: T
  optional: true
  description: Generate a Bed Topology Report
  values:
  - type: bool

- tag: H
  optional: true
  description: Set the square width and height of the area to probe.
  values:
  - tag: linear
    type: float

- tag: F
  optional: true
  description: Set the front limit of the probing grid.
  values:
  - tag: linear
    type: float

- tag: B
  optional: true
  description: Set the back limit of the probing grid.
  values:
  - tag: linear
    type: float

- tag: L
  optional: true
  description: Set the left limit of the probing grid.
  values:
  - tag: linear
    type: float

- tag: R
  optional: true
  description: Set the right limit of the probing grid.
  values:
  - tag: linear
    type: float

- tag: J
  optional: true
  description: Jettison the leveling data stored in SRAM and turn off leveling compensation. Data in EEPROM is not affected.
  values:
  - type: bool

- tag: V
  optional: true
  description: Set the verbose level. Level 2 and up act like 'T'.
  values:
  - type: int
    tag: 0-4

examples:

- pre: Automatic Probing examples
  post: '`G29` is most commonly used without any arguments. This uses the defaults set in `Configuration.h`.'
  code: G29 ; probe and enable

- post: Probe a 5x5 matrix.
  code: G29 P5 ; 5x5 matrix

- post: 'Probe a 4x8 matrix from `X50` `Y50` to `X150` `Y150`, printing a full report.'
  code: G29 X4 Y8 L50 R150 F50 B150 T V4

- pre: Manual Probing example
  post: 'Each `G29` command goes to the next step until the whole procedure is done. The `V1` parameter provides a progress report.'
  code:
  - G29 V1 ;  Ready!  Go to Point 1, wait...
  - G29 V1 ; Store Z, go to Point 2, wait...
  - G29 V1 ; Store Z, go to Point 3, wait...
  - G29 V1 ; Store Z, go to Point 4, wait...
  - G29 V1 ; Store Z, go to Point 5, wait...
  - G29 V1 ; Store Z, go to Point 6, wait...
  - G29 V1 ; Store Z, go to Point 7, wait...
  - G29 V1 ; Store Z, go to Point 8, wait...
  - G29 V1 ; Store Z, go to Point 9, wait...
  - G29 V1 ; Store Z. Calculate matrix. Activate.

---

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`](/docs/gcode/G028.html) 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
{% 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](#usage-g029g2) 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](/docs/gcode/G029-ubl.html) 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`](/docs/gcode/M500.html) to save the leveling data to EEPROM, if desired.

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

  1. Find and select the `Level Bed` menu item and verify your choice. (The location of this menu item differs depending on your controller and Marlin version.)
  2. Wait for `Homing XYZ` to complete.
  3. When `Click to Begin` appears, press the controller button to move to the first point.
  4. Repeat the following steps until the entire mesh is completed:
    - Use the controller wheel to adjust Z so that a piece of paper can just pass under the nozzle.
    - Press the controller button to save the Z value and move to the next point.
  5. Use `Control` > `Save to EEPROM` to save the mesh to EEPROM.

{% enddetails %}
