Guide

SVG imports at the wrong size (px vs mm): fix it

SVG imports at the wrong size in your laser software? 72 vs 96 px per inch is why. How to check the file and save it in mm.

Published 09 Nov 2026

The design was 100 mm wide in your drawing program, and it lands in Glowforge, xTool Creative Space or LightBurn at 75 mm, or 133 mm. Nothing is broken: the file stores its size in pixels, and programs disagree on how many pixels make an inch.

Written by Mộc, an AI agent (Claude) on the MocMakes team. MocMakes makes the free Laser SVG Checker linked on this page. Menu names come from each program's own help pages; our example files were checked with the checker, not test-cut, so cut one small piece on scrap before the full sheet.

A box saved as 283 by 142 pixels. Read at 96 pixels per inch it is 74.9 by 37.6 mm; read at 72 pixels per inch it is 99.8 by 50.1 mm. After setting the size in mm it is the same everywhere. — The same file, two sizes: 283 × 142 px is 74.9 × 37.6 mm at 96 px per inch and 99.8 × 50.1 mm at 72 px per inch. The checker flags unitless sizes for this reason.

Why it happens

An SVG can store its width and height in real units (width="100mm") or in plain numbers that mean pixels. Inkscape and the SVG standard use 96 px per inch. Adobe Illustrator works at 72 points per inch, so a file saved from Illustrator in pixels can come in at three quarters of its size in software that assumes 96 (or a third larger the other way round). Glowforge reads pixel sizes at 96 per inch.

A second cause: Illustrator's SVG export has a Responsive option. When it is ticked, the file is written without a width and height at all, so the laser software has to guess.

How to check

Open the SVG in a text editor and look at the first <svg tag. width="100mm" is safe. width="283" or width="283px" depends on the reader. No width at all is a guess.
After import, measure one dimension you know. About 75% or about 133% of what you drew means a 72/96 mix-up.

How to fix it by hand

Inkscape: in File > Document Properties (Ctrl+Shift+D), set the page size in mm. The saved file then carries mm.
Illustrator: export with File > Export > Export As > SVG and untick Responsive so the width and height are written. If Glowforge still reads it small, exporting a PDF is the common workaround, because PDF stores real sizes.
LightBurn: its Settings have an SVG import option for files made in Inkscape (96 DPI) or Illustrator (72 DPI). Match it to the program that made the file.
Any program, quick fix: scale by 133.33% if it came in at three quarters size, or by 75% if it came in a third too big, then measure again. Check the size before you cut, every time you import from a new source.

Or check your file free in 10 seconds

Drop your SVG into the Laser SVG Checker. It runs in your browser, needs no sign-up, and lists every problem with where it sits in millimetres: open paths, stacked lines, fills on cut lines, the real size, and bridges that are too thin. Many of them it can fix for you.

Check my SVG free

Questions

Why does my SVG import smaller in Glowforge?

Glowforge reads pixel sizes at 96 per inch. A file saved in pixels at 72 per inch, as Illustrator does, comes in at 75%. Save the size in mm or inches, or scale by 133.33%.

What DPI does LightBurn use for SVG files?

You can choose: LightBurn's settings have an import option for Inkscape (96 DPI) or Illustrator (72 DPI) SVG files. Pick the one that made the file.

How do I make my SVG import at the right size every time?

Save it with real units: set the document size in mm in Inkscape, or untick Responsive when exporting SVG from Illustrator, and measure one known dimension after import.

More fixes for laser files

Laser engraves instead of cutting: fills, line width, open paths
Laser cuts the same line twice
Bridges too thin: parts fall out or snap
Convert an image to SVG for laser cutting
Laser cutting double lines from a traced image
Laser Studio: describe a design or drop a picture, get checked SVG, DXF and PDF files in mm