FractionA ruler you can print
Six inches in 16ths and fifteen centimetres in millimetres, drawn in physical units so paper reproduces them at true size. Print at 100% scale (never “fit to page”), check the calibration bar against any bank card, cut along the top edges.
Set the print dialog to 100% scale — never “fit to page” — then check the calibration bar.
Inches — 16ths
Centimetres — millimetres
Calibration
This bar is exactly the width of a standard bank card — 85.60 mm (ISO/IEC 7810). After printing, lay a card on it: if they match, the rulers above are true.
Common questions
- How do I make sure it prints at the right size?
- In the print dialog set the scale to 100% — not “fit to page” — then lay any bank card on the calibration bar. A standard card is exactly 85.60 mm wide, and if the bar matches the card, the rules above it are true.
- How accurate is a paper ruler?
- Good enough for layout and homework, not for machining: printers hold size to a fraction of a millimetre across 15 cm, and paper moves with humidity. For work that needs better, use a real rule — and this page’s charts to convert what it says.
- Why do the inch marks get shorter as the fractions get finer?
- That is how real rules are engraved: length encodes the denominator. The longest interior marks are halves, then quarters, eighths, and sixteenths — count which halving you are in and that is the bottom of the fraction.