Download A4 test sheet (PDF) Download US Letter test sheet (PDF)
How to run the test
- Print at actual size. In the print dialog choose Actual size, 100% or Default scale. Turn off Fit to page, Shrink to fit and Scale to fit. In Acrobat that is Size: Actual size; in macOS Preview untick Scale to Fit; in Firefox set Scale to 100%.
- Measure the printout. Lay a physical ruler on the 100 mm line, the 100 mm vertical line, and the 4 inch line.
- Read the result. About 100 mm means the page printed at true size. Noticeably shorter or longer means something rescaled it.
Is it the PDF or the printer?
Two different things can go wrong. The PDF can contain the wrong size, or the printer can rescale a correct PDF to fit. Open the test sheet in PdfRuler and measure the line: it will read exactly 100 mm, because that is what the file says. If your paper then measures something else, the printer or its settings scaled it. The same check works for your own files: measure in PdfRuler first, print second.
Fix a wrong scale
Divide 100 by the length you measured, multiply by 100, and enter that as a custom scale. A 96 mm line needs 104.2%. Print again and re-measure. Keep margins in mind: if the page does not fit the printable area at 100%, some printers shrink it unless you choose actual size.
More: how to find a PDF's page size, why a PDF prints smaller than 100%, print-ready checklist and the paper size reference.
Frequently asked questions
Why does my PDF print smaller than it looks on screen?
Most often the print dialog is set to Fit, Shrink to fit or Scale to fit. That rescales the page to the printable area and a 100 mm line comes out shorter. Choose 100%, Actual size or Default scale instead.
How accurate should the printed lines be?
Within about 0.5 mm over 100 mm on a good printer. Paper can also stretch slightly with heat and humidity. A difference of 2 mm or more means the page was rescaled.
Does this test prove my PDF is the right size?
No, it separates two problems. Open the PDF in PdfRuler to see what the file itself says; the test sheet shows what your printer does with a file. If PdfRuler reads 100 mm but the paper reads 96 mm, the printer scaled it.
What scale should I enter to correct it?
Divide 100 by the length you measured and multiply by 100. A line that measures 96 mm needs about 104.2%. Print again at that custom scale and re-measure.
