How do I convert laser settings from a 10 W to a 20 W laser?

Keep the energy per millimetre the same. Energy per mm is power × power fraction × passes ÷ speed. With the same power percentage and passes, doubling the optical power lets you roughly double the speed: 10 W at 80 % and 360 mm/min becomes about 720 mm/min on a 20 W laser of the same type. Treat it as a starting point and run a test grid.

Can I convert diode laser settings to a CO2 laser?

Not reliably. A diode laser emits blue light around 450 nm and a CO2 laser emits infrared light at 10.6 µm, and materials absorb the two very differently. Clear acrylic, for example, cuts cleanly on a CO2 laser but lets most of a diode beam pass through. Start from settings made for the same laser type.

What is the S-value in LightBurn and how does it relate to power %?

On GRBL-based lasers, power is sent as an S-value. Power % is the S-value divided by the S-value max, which must match the controller’s $30 setting (1000 on current GRBL, 255 on older versions). If they do not match, the laser may run at only a fraction of the power you asked for.

How do I convert mm/min to mm/s for laser speed?

Divide mm/min by 60 to get mm/s, and multiply mm/s by 60 to get mm/min. For inches per minute, multiply by 25.4 to get mm/min. Diode lasers on GRBL often show speed in mm/min, while many CO2 controllers use mm/s.

Laser Power & Speed Converter Between Machines (J/mm)

How the conversion works

A laser removes or marks material by putting energy into it. If two lasers of the same type deliver the same energy to each millimetre of the line, they should produce a similar cut or mark. That energy is:

Line energy (J/mm) = optical power (W) × power fraction × passes ÷ speed (mm/s)

When you engrave a filled area, the head scans back and forth with a small gap between lines, so the energy spreads over an area:

Area energy (J/mm²) = optical power (W) × power fraction × passes ÷ (speed (mm/s) × line interval (mm))

The converter works out this energy for the settings that worked, then solves the same equation for your machine — either the speed for the power you want to use, or the power for the speed you want to use.

Worked example: cutting

	Settings that worked	Your machine
Laser	10 W diode	20 W diode
Power	80 %	80 %
Speed	360 mm/min (6 mm/s)	≈ 720 mm/min (12 mm/s)
Passes	1	1
Line energy	10 × 0.8 ÷ 6 ≈ 1.33 J/mm	20 × 0.8 ÷ 12 ≈ 1.33 J/mm

The numbers are only an illustration of the arithmetic, not a recommended setting for any material.

Worked example: engraving with DPI

Line interval is the distance between scan lines. If your software asks for DPI instead, the interval is 25.4 ÷ DPI mm, so 254 DPI is 0.1 mm. With 10 W at 30 %, 100 mm/s and a 0.1 mm interval, the area energy is 10 × 0.3 ÷ (100 × 0.1) = 0.3 J/mm².

Why the result is only a starting point

Spot size and intensity. Two lasers with the same J/mm but different spot sizes put different power into each square millimetre. A smaller spot can char or cut where a larger one only marks.
Rated vs real power. Use the optical output power. Some diode modules are listed by electrical input power, which is several times higher, and laser tubes lose power as they age.
Wavelength. Diode, CO2 and fiber lasers are absorbed differently by the same material. The converter warns you when the two laser types differ, because matching energy does not carry over.
Very low power. Below about 10 %, many lasers fire unevenly. If the result asks for very low power, raise the speed or reduce the passes instead.
Everything else. Focus height, air assist, the lens, and the material batch all change the result. Run a small test grid on scrap and adjust from there.

Units cheat sheet

From	To	Do this
mm/min	mm/s	÷ 60
mm/s	mm/min	× 60
in/min (IPM)	mm/min	× 25.4
in/s	mm/s	× 25.4
S-value	power %	S ÷ S-value max × 100
DPI	line interval (mm)	25.4 ÷ DPI

FAQ

How do I convert laser settings from a 10 W to a 20 W laser?: Keep the energy per millimetre the same. Energy per mm is power × power fraction × passes ÷ speed. With the same power percentage and passes, doubling the optical power lets you roughly double the speed: 10 W at 80 % and 360 mm/min becomes about 720 mm/min on a 20 W laser of the same type. Treat it as a starting point and run a test grid.
Can I convert diode laser settings to a CO2 laser?: Not reliably. A diode laser emits blue light around 450 nm and a CO2 laser emits infrared light at 10.6 µm, and materials absorb the two very differently. Clear acrylic, for example, cuts cleanly on a CO2 laser but lets most of a diode beam pass through. Start from settings made for the same laser type.
What is the S-value in LightBurn and how does it relate to power %?: On GRBL-based lasers, power is sent as an S-value. Power % is the S-value divided by the S-value max, which must match the controller’s $30 setting (1000 on current GRBL, 255 on older versions). If they do not match, the laser may run at only a fraction of the power you asked for.
How do I convert mm/min to mm/s for laser speed?: Divide mm/min by 60 to get mm/s, and multiply mm/s by 60 to get mm/min. For inches per minute, multiply by 25.4 to get mm/min. Diode lasers on GRBL often show speed in mm/min, while many CO2 controllers use mm/s.

Sources

LightBurn documentation, Common GRBL setups (S-value max and GRBL $30) and GRBL low or no power output.
xTool, Types of laser engravers explained (diode, CO2 and fiber wavelengths).
Creality Falcon, How to cut clear acrylic with a diode laser (why clear acrylic is hard for a diode).

Last checked 2026-10-26

Laser power & speed converter

1Settings that worked

2Your machine