LPI, Line Interval & DPI Calculator

Convert lines per inch to line interval in millimetres and check whether your image has enough pixels for the size you want to engrave.

lines/in

LightBurn calls the same value DPI.

mm

Spacing between raster scan lines.

mm
mm
Check my image (optional)

Resolution results

Line interval
0.100mm
LPI / DPI
254.0lines/in
Image pixels needed
1,000 × 1,000px
For 1 image pixel per scan line without interpolation.
Add your image pixel dimensions under “Check my image” to test for upscaling.

Results are starting points, not guarantees. Lasers can start fires and damage eyes — follow your machine’s safety instructions and never leave a running laser.

Quick answer

Line interval (mm) = 25.4 ÷ LPI. For example, 254 LPI is a 0.1 mm line interval. LightBurn uses the same relation and calls it DPI. To engrave 100 mm wide at 254 DPI without upscaling, your image needs 1000 pixels across.

How to use

  1. Enter LPI or line interval (the other updates).
  2. Enter the engraving size.
  3. Optional: enter your image’s pixel size to see if it will be upscaled.

Worked example

254 LPI → 0.100 mm. 100 mm × 100 mm at 254 DPI needs 1000 × 1000 px. An image of 800 px across printed 100 mm wide has an effective 203 DPI, so it would be upscaled.

How it’s calculated

interval = 25.4 ÷ LPI · pixels needed = size (mm) ÷ 25.4 × DPI, rounded up · effective DPI = pixels ÷ (size in mm ÷ 25.4).

Frequently Asked Questions (FAQ)

What LPI should I use for photos?

It depends on your laser's spot size and the material; there is no single best number. Run a test card that varies the line interval (LightBurn's material test can vary "Interval") and pick the cleanest result.

Is DPI the same as LPI?

In LightBurn's image settings, DPI = 25.4 ÷ line interval, so for laser scanning they are the same number.

Does a smaller line interval always look better?

No. If lines overlap too much, the material overburns and detail can be lost. Test it.

Sources

Last reviewed: 2026-10-26

Built and maintained by Numberwright. Every formula on this page is listed under “How it’s calculated”, with its sources. Found a mistake? Contact details coming soon.

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