Printable Ruler, Actual Size: Calibrate the Print With a Bank Card
Print a ruler at actual size on US Letter or A4, in inches with 1/16 marks, centimetres with mm marks, or both edges. A bank card box corrects the printer scale. Runs in your browser.
Your choices stay in this browser. Nothing is uploaded or sent to a server. This is a printable ruler, not a calibrated measuring instrument.
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Report a problem or suggest an improvement
Nothing is sent until you press Send. Your measurements are included only if you tick the box, and you can see the full report below first.
When to use this
- You need a ruler and only have a printer.
- A printable ruler you found online printed a few percent too small or too large and you want to fix that.
- You want a quick protractor or a ruler with both inch and millimetre edges for a craft or school project.
How to use
- Choose the units, the paper, the page orientation, the ruler length and, if you like, a protractor.
- Press Make ruler and print the page at 100 percent (Actual size). Do not use Fit to page.
- Hold a bank card against the printed card box, measure the box and type its width. Press Make ruler again.
- Print the corrected page. Check the card against the box once more before you rely on the ruler.
Examples
- A box that printed at 84.0 mm: A standard bank card is 85.60 mm wide. If the printed box measures 84.0 mm, the correction factor is 85.6 / 84.0 = 1.019, so the corrected page is drawn about 1.9 percent larger.
- Longest ruler per page: The tool keeps the drawing inside the page with 15 mm (0.6 in) kept free on every side. In landscape that leaves room for 9 in on US Letter and 26 cm on A4.
- Both edges: Pick Both edges for a strip with inch marks in 1/16 steps on one edge and millimetre marks on the other, drawn for the same physical length.
Understanding the result
Every mark is placed in millimetres from the zero line: an inch mark every 25.4 mm with 1/16 marks between, a millimetre mark every 1 mm. The card box is drawn 85.60 mm (3.370 in) wide, the ISO/IEC 7810 ID-1 card width. Your measurement of the printed box gives the correction factor (85.6 divided by what you measured), and the whole drawing is scaled by it, so the next print should come out at the right size. If you check a corrected print and it is still off, choose that option and the new factor is multiplied with the old one.
Assumptions this tool makes
- A bank card is 85.60 mm by 53.98 mm (ISO/IEC 7810 ID-1). Cards from other schemes or very worn cards may differ slightly.
- The printer scales the whole page by the same amount in both directions. Some printers scale the two directions differently.
- Your page margins in the print dialog are Default or smaller than 15 mm (0.6 in).
Limitations
- This is not a calibrated or certified measuring instrument. Printer scaling and paper stretch vary between printers, settings, paper and even prints, and humidity changes paper size.
- The correction only fixes the print you checked with the card. It does not promise any accuracy beyond that card check, so check again after every new print.
- The ruler is limited to what fits on one page. Use a tape measure or a real ruler for long, expensive or safety-related measurements.
- Fit to page, a print scale other than 100 percent, or a different paper or orientation in the print dialog will make the ruler wrong. Check the card box each time.
FAQ
How do I print a ruler at actual size?
Choose Print on the page, set the scale to 100 percent or Actual size, turn off Fit to page and Shrink to fit, set margins to Default and choose the same paper and orientation as in the tool. Then check the card box with a real bank card.
Why does a printed ruler come out too small or too large?
Print dialogs often shrink a page to fit the printable area, and some printers add their own scaling. That changes every length on the page by the same percentage, which is why one known length, a bank card, is enough to measure it.
How does the credit card calibration work?
The page prints a box exactly as wide as a standard bank card, 85.60 mm or 3.370 in. You measure the printed box. The tool divides 85.6 by your number and scales the next page by that factor, for example 85.6 / 84.0 = 1.019.
Should I also change the print scale to 101.9 percent?
No. Either print the uncorrected page at 101.9 percent, or print the corrected page at 100 percent. Doing both corrects twice and makes the ruler wrong the other way.
Is a printed ruler accurate enough for measuring?
It is good for rough everyday measuring after you check it against a card. It is not a calibrated instrument and printer scaling and paper stretch vary, so do not use it where an exact or certified measurement matters.
Are my numbers sent anywhere?
No. The ruler is drawn in your browser and nothing you type is uploaded or sent to a server.
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