How do I make a laser test grid without LightBurn?

Set the power range, the speed range (or line interval range) and the cell size above, then download the G-code for a GRBL laser or the SVG. The G-code runs in any GRBL sender, including LaserGRBL. The SVG gives every cell its own LightBurn layer colour, so in LightBurn or xTool Creative Space you only have to type each cell’s power and speed from the numbered table.

What power and speed range should a material test cover?

Wide enough that the weakest cell barely marks and the strongest one clearly overburns; the right setting is then somewhere inside. This page starts at 20–100 % power against 1,000–5,000 mm/min, a 25× spread in energy. Run it on scrap of the exact material, and narrow the range for a second, finer grid around the cells you like.

Why does the grid use M4 and not M3?

In GRBL’s laser mode, M4 scales power with the actual speed, so the ends of each fill line, where the head slows down, do not get extra energy. M3 keeps power constant and overburns where the head slows. M4 needs laser mode on ($32=1) and GRBL 1.1f or later, according to LightBurn.

What is J/mm and why are the cells coloured by it?

J/mm is the energy put into each millimetre of a line: optical power × power % × passes ÷ speed in mm/s. For a filled cell, dividing by the line interval gives J/mm². Cells with the same J/mm² are expected to burn about the same on the same laser type, so the colours show which cells should look alike before you burn them. It is a model, not a measurement.

Generator · test grid

Laser material test grid generator

Build a power × speed test grid in your browser and watch a laser head burn it cell by cell, shaded by the energy each cell gets. Then download GRBL G-code to run it, or an SVG with one LightBurn layer colour per cell. Switch to a line-interval grid or a grayscale strip for engraving.

1What to test

Grid

Power × speedPower × line intervalGrayscale strip

Job

Engrave (fill)Cut / line

Machine (sets the optical power)

Optical power (W, optional)

The laser’s optical output, not the electrical input. Leave blank to colour by relative energy.

S max = your $30

GRBL turns S into power on a 0–$30 scale. Check $30 with $$; LightBurn’s S-value max should be the same number.

2Grid and settings

Power from (%)

to (%)

Columns

Unit

Speed from

Rows

Line interval (mm)

Passes

Cell size (mm)

Gap (mm)

Grid origin X (mm)

Grid origin Y (mm)

Bottom-left corner of the grid in your work coordinates. The file uses absolute moves (G90).

Cells

5 × 5

Energy range

0.24–6J/mm²

Burn time

4:07

laser-on time only

Grid size

38 × 38mm

3,033 G-code lines

0.24Lighter = less energy · darker = more (log scale)6 J/mm²

Numbers = burn order, weakest first. The head speed is drawn relative to each row’s speed.

J/mm compares settings only between lasers of the same type. A diode, CO2 and fiber laser burn the same material very differently.

3Before you run the G-code

Laser mode on: send $$ and check $32=1. The file uses M4 (dynamic power), which needs laser mode; with it off GRBL pauses at every power change and leaves burn spots.
$30 matches: this file assumes $30=1000. If your $30 is different, change “S max” above, or the power will be wrong.
Focus and origin: the file has no Z moves and does not home. Set the focus / Z height first, and set the work origin at the grid’s bottom-left corner. Frame the job before you fire.
Start small, on scrap: the weakest cell runs first. If the first cells already char deeply, stop and lower the range.
Stay with the machine: test grids put a lot of heat into a small area. Keep a fire extinguisher or fire blanket in reach and use air assist if you have it.
Ventilate and protect your eyes: run the exhaust, and wear glasses rated for your laser’s wavelength.

I have checked $32, $30, focus and the origin

Labels in the SVG (layer 00, black)

G-code check: 3,033 lines · S 200–1000 · X 0–38 · Y 0–37.95 mm · no laser-on rapid moves

The SVG is for LightBurn, xTool Creative Space and similar software: give each colour (layer) the power and speed from the numbered table. LightBurn matches imported colours to its layer palette.

First lines of the G-code

; BEAM SETTINGS material test grid
G21 ; millimetres
G90 ; absolute coordinates
M5 S0
M4 S0 ; dynamic laser power (needs $32=1)
; cell 1: power 20% S200 F5000 interval 0.1 mm (actual 0.1 mm)
G0 X0 Y32.05 S0
G1 X6 S200 F5000
G0 X6 Y32.15 S0
G1 X0 S200
G0 X0 Y32.25 S0
G1 X6 S200
G0 X6 Y32.35 S0
G1 X0 S200
G0 X0 Y32.45 S0
G1 X6 S200
G0 X6 Y32.55 S0
G1 X0 S200
G0 X0 Y32.65 S0
G1 X6 S200
G0 X6 Y32.75 S0
G1 X0 S200
G0 X0 Y32.85 S0
G1 X6 S200

The formulas

Line energy E [J/mm] = optical power [W] × power % ÷ 100 × passes ÷ speed [mm/s]

Area energy E_a [J/mm²] = E ÷ line interval [mm]

S value = power % ÷ 100 × $30 · F [mm/min] = speed [mm/s] × 60

These are the same energy formulas as our power and speed converter. The cells are shaded on a log scale between the weakest and strongest cell, because a test grid usually spans 10× or more in energy. With no optical power entered, the shading uses power % ÷ speed, which ranks the cells the same way.

The G-code is written for GRBL 1.1: millimetres (G21), absolute moves (G90), M4 dynamic power, then each cell filled with back-and-forth lines at your interval. Moves between lines are G0, and GRBL’s laser mode turns the laser off on G0. There are no Z moves and no homing; the file ends with M5. Cells run weakest first, the same order LightBurn’s Material Test uses (highest speed, lowest power, first), so you can stop early if the first cells already burn too hard.

Reading the result

Pick the weakest cell that gives the look you want. More energy than that only adds heat, smoke and time.
Look along a diagonal. Cells with similar shading should look similar. Where they do not, the material is not responding linearly — for example at very low power, where a laser can fire unevenly, and at very high speed, where the head may not reach the set speed inside a small cell.
For fills, test the interval too. The power × line interval grid shows when lines start to leave gaps or overlap; our line interval and DPI calculator gives a starting interval from your spot size.
Moving the result to another machine. Use the J/mm² of the cell you liked in the converter, but only between lasers of the same type, and run a small grid again.

Before the first run

A test grid is a lot of energy in a small area, so it is the job most likely to flare up. Check $32=1 and $30 with our GRBL $$ settings checker, keep away from the materials on our what not to laser cut list, run an exhaust (see the exhaust fan calculator), and wear glasses rated for your wavelength.

Other ways to make a test grid

Software	Test grid
LightBurn	Built-in Material Test (paid software): varies power, speed, interval, passes and, where the laser supports it, frequency; labels rows with speed and columns with power.
xTool Creative Space	Material Test Array in xTool’s own software for xTool machines (newer xTool support pages call the software xTool Studio).
LaserGRBL	Free. Generate → Power vs Speed Test makes a power and speed grid as G-code, according to a laser maker’s tutorial (Longer); not checked in LaserGRBL’s own documentation.
This page	Free, runs in the browser, shades the cells by energy before you burn, and writes GRBL G-code, a layered SVG and a numbered table. No account or email.

FAQ

How do I make a laser test grid without LightBurn?: Set the power range, the speed range (or line interval range) and the cell size above, then download the G-code for a GRBL laser or the SVG. The G-code runs in any GRBL sender, including LaserGRBL. The SVG gives every cell its own LightBurn layer colour, so in LightBurn or xTool Creative Space you only have to type each cell’s power and speed from the numbered table.
What power and speed range should a material test cover?: Wide enough that the weakest cell barely marks and the strongest one clearly overburns; the right setting is then somewhere inside. This page starts at 20–100 % power against 1,000–5,000 mm/min, a 25× spread in energy. Run it on scrap of the exact material, and narrow the range for a second, finer grid around the cells you like.
Why does the grid use M4 and not M3?: In GRBL’s laser mode, M4 scales power with the actual speed, so the ends of each fill line, where the head slows down, do not get extra energy. M3 keeps power constant and overburns where the head slows. M4 needs laser mode on ($32=1) and GRBL 1.1f or later, according to LightBurn.
What is J/mm and why are the cells coloured by it?: J/mm is the energy put into each millimetre of a line: optical power × power % × passes ÷ speed in mm/s. For a filled cell, dividing by the line interval gives J/mm². Cells with the same J/mm² are expected to burn about the same on the same laser type, so the colours show which cells should look alike before you burn them. It is a model, not a measurement.

Sources

LightBurn, Material Test (parameters, run order, speed-unit warning) and Layer colors (palette 00–29; imported colours are matched to it).
LightBurn, GRBL configuration ($32 laser mode, M4 on GRBL 1.1f or later) and GRBL low or no power output ($30 and S-value max must match).
Grbl wiki, Laser mode (M3 and M4, laser off on G0) and Configuration ($30–$32).
xTool support, Material Test Array; Longer, Power vs Speed Test with LaserGRBL (a maker’s tutorial: Generate → Power vs Speed Test).

Last checked 2026-11-01 · Calculated values and generated files; no laser was used to make this page. Check the G-code in your sender before running it.