Check your printer
Do this once per printer. Print the check sheet at 100% and measure the bar. If it’s 100 mm, every card you make from now on comes out the right size.
This tool’s whole job is to make a pattern exactly the right physical size for a particular pair of eyes at a particular distance. The file we give you is exact. The one thing we can’t see is your print dialog — and by default it often shrinks the page a few percent to fit a margin it assumes you need. That silently undoes the sizing.
So: check once, here, with a ruler. It takes two minutes and you never have to think about it again.
How to do it
- Download the check sheet for your paper size (above). It’s made in your browser — nothing is uploaded, and it works offline.
- Print it with scaling off. In the print dialog choose“Actual size” / “100%” / “Custom scale: 100”. Never “Fit to page”, “Shrink oversized pages” or “Scale to fit”.
- Measure the black 100 mm bar end to end with a ruler. A ruler graded in millimetres is ideal.
- 100 mm (within about ±0.5 mm) means you’re good. Spot-check the 4 inch bar too — it should read 101.6 mm.
If it measures short (a very common ~96% or ~94%), it is almost always the print dialog, not the file. Turn off “Fit to page”, set the scale to exactly 100%, and print again. Some drivers also have a “borderless” or “page scaling” option worth checking.
If it still won’t print true, note the measured length and your printer model. A printer that reliably prints, say, 96 mm instead of 100 mm is scaling by a fixed factor, and you can compensate by setting your print dialog’s custom scale to the inverse — but fixing the setting is always better than compensating for it.
What’s on the sheet
- A 100 mm bar — the main measurable.
- A 4 inch bar (101.6 mm), as a cross-check in imperial.
- Centimetre and inch rulers, so you can check the whole span, not just two ends.
Why the cards themselves don’t carry a bar
They can — there’s a “Show 100 mm scale bar” switch in the generator’s Advanced settings. It’s off by default because a printed card works by giving the eye one clear, bold thing to find, and a ruler in the corner is a second thing competing for that attention. Scale is a property of your printer, not of each card, so it’s better checked once — here — than re-proved on every sheet.
Multi-sheet (tiled) posters are the exception: their assembly-instructions page always carries a 100 mm bar, because that’s the page you measure before trimming a dozen sheets.