A printable ruler that is actually the right size
This printable ruler draws a centimetre/millimetre ruler, an inch ruler divided into sixteenths, or both on one strip, at true scale: every millimetre tick is placed exactly 1 mm apart in the PDF, so a correctly printed sheet measures as accurately as a plastic ruler. Choose 10, 15, 20 or 25 cm (4 to 10 in) to print in one piece, or 30 cm / 12 in as two halves you join with the alignment marks.
Because a printed ruler is only as accurate as the print scaling, every sheet includes a 50 mm (1.97 in) scale-check square. Measure it with anything you trust — a coin, a bank card (85.6 mm wide), a known screw — and you will know at once whether the printer scaled the page. An optional 180° protractor with 1° ticks completes a basic geometry set for homework, sewing, model making or checking a parcel against a size limit.
The ruler is drawn in your browser from exact measurements; nothing is uploaded.
How to use the Printable Ruler
- Choose the Units: centimetres and millimetres, inches with 1/16 divisions, or both scales on one strip (cm along the top edge, inches along the bottom).
- Pick a Length. Up to 25 cm / 10 in prints as a single strip; 30 cm and 12 in print as two halves with “join here” marks.
- Set Rulers per page if you need several (for a class, say), the Paper size, and leave Orientation on Auto — long rulers switch to landscape automatically.
- Keep the scale check on and add a protractor if you want one.
- Press Print or Download PDF. In the print dialog choose 100% / Actual size and turn off “Fit to page” or “Shrink to printable area”. Then measure the check square.
Printable Ruler features
True-scale ticks
Millimetre ticks every 2.8346 pt and inch ticks every 72 pt in a vector PDF — not a scaled bitmap. Every 5 mm and 1 cm, and every ½, ¼, ⅛ and 1/16 in, has its own tick length so the ruler reads like a real one.
Joinable 30 cm and 12 in rulers
Longer than a page allows, so they print as two halves — the second numbered from 15 to 30 (or 6 to 12) — with marks showing where to overlap and tape.
Scale-check square
A 50 mm square with its inch equivalent and an explanation of what to do if it comes out the wrong size.
180° protractor
10 cm across with ticks every degree, labels every 10° reading both ways, a baseline and a centre mark — print, cut along the arc and use.
Several rulers per page
Print up to six strips on one sheet for a classroom, a workshop drawer or a sewing kit.
High-resolution outputs
The PDF is vector; the PNG is rendered at 300 dpi (3508 × 2480 px for A4 landscape) for printing from an image or a phone.
Why printed rulers come out the wrong size — and how to fix it
Browsers and PDF viewers often shrink pages by 3–8% to keep the content inside the printer’s margins. The ruler is drawn exactly, but “Fit to page” scales it down. Set scaling to 100% / Actual size / None, make sure the paper size in the dialog matches the one chosen here, and check the square.
| Check square measures | What it means | Fix |
|---|---|---|
| 50 mm | Printed at true scale | None — the ruler is accurate |
| 47–49 mm | Shrunk to fit margins (94–98%) | Choose “Actual size” / 100%, disable “Fit to printable area” |
| Over 50 mm | Enlarged — often Letter content printed on A4 with scaling | Match the paper size setting to the sheet in the tray |
| Right width, wrong height | Rare printer feed error | Try another tray or print the PDF from a different app |
Reading the scales
- cm/mm ruler: the long ticks with numbers are centimetres, the medium ticks are half-centimetres (5 mm) and the short ticks are millimetres. 1 cm = 10 mm; 2.54 cm = 1 inch.
- Inch ruler: the longest ticks are inches, then halves, quarters, eighths and sixteenths in decreasing length. 1/16 in ≈ 1.6 mm.
- Both: centimetres read along the top edge, inches along the bottom, with the two scales aligned at zero — handy for converting as you measure. For exact conversions use the length converter.
- Protractor: place the centre mark on the vertex of the angle and the baseline along one arm; read where the other arm crosses the arc. The inner numbers run the opposite way for angles opening to the left.
- Paper rulers are fine for homework, sewing, packaging checks and a quick measurement of a phone screen; for machining or anything under ±0.5 mm, use a steel rule. Checking print DPI instead? Try the DPI calculator.
Printable Ruler FAQ
Is this printable ruler accurate?
The PDF is exact: 1 mm per millimetre tick. Accuracy then depends entirely on printing at 100% scale, which is why a 50 mm check square is printed alongside. If the square measures 50 mm, the ruler is as accurate as the paper’s expansion allows (well under 0.5 mm over 30 cm).
Why can’t I print a 30 cm ruler in one piece?
A4 is 297 mm long and Letter 279 mm, and printers cannot print to the very edge. A 30 cm (or 12 in) ruler therefore prints as two halves; overlap them at the join marks and tape the back. 25 cm / 10 in fits in one piece in landscape.
Can I print the ruler from my phone?
Yes — download the PDF and print it from the phone’s share menu, choosing 100% or Actual size. Phone print dialogs often default to “Fit”, so check the square afterwards.
What is the best paper for a printable ruler?
Card (160–200 gsm) keeps its edge straight; plain paper works if you glue it to a strip of cardboard or the edge of a notebook. Cut exactly along the printed edge of the ruler for accurate measuring from zero.
Does the on-screen preview show the real size?
No. The preview is scaled to fit your window, so measuring the screen is meaningless. Only the printed page or the PDF opened at 100% is true size.
Which paper sizes are supported?
A4 (210 × 297 mm) and US Letter (8.5 × 11 in), portrait or landscape; Auto picks landscape when the ruler is too long for portrait. The paper size converter lists other sizes.