To Scale Ruler

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Still deciding on the Scale Ruler Printables?

• True-size rulers (PDF)
• Architect scales (PDF)
• Metric scales (PDF/XLSX)
• Calibration check (PDF)

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Free printables

Single sheets you can print right now, no sign-up. The full pack adds every sheet in one download plus the editable files.

True-Size Ruler Printable1 page · free PDFPrintable Architect Scale Strips1 page · free PDFPrintable Metric Scale Reference Chart1 page · free PDFPrintable Calibration Check Sheet1 page · free PDF

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Why screen rulers need calibrating

Web pages measure in CSS pixels, and a CSS pixel is a different physical size on every device — a phone, a laptop and a large monitor all show “1 cm” at different real sizes. The only reliable way to get a true-size ruler on screen is to calibrate it against something whose size you know. A standard bank or ID card (the ISO/IEC 7810 ID-1 size used worldwide) is 85.60 mm × 53.98 mm, so matching the dashed box to your card tells the ruler how many pixels make a millimetre.

How to use the ruler

1. Hold a bank card, library card or ID card flat against the screen, lined up with the left edge of the dashed box.
2. Drag the calibration slider until the box is exactly as wide as the card.
3. The ruler now shows true centimetres and millimetres, or inches in sixteenths.
4. Pick a scale to read real-world distances from plans or maps.
5. Enter a length you measured on a drawing to convert it to the real size.

Your calibration is remembered on this device so you only need to do it once, unless you change the browser zoom or display.

Common drawing and map scales

Worked example

On a building plan at 1:100, a wall measures 4.5 cm with the calibrated ruler. Its real length is 4.5 × 100 = 450 cm, or 4.5 m. On a US plan at 1/4 inch = 1 foot, a room that measures 3 1/2 inches on paper is 3.5 × 4 = 14 feet long. Always check the scale printed on the drawing — and that the drawing hasn’t been printed at a different size than intended.

Printed drawings and the “do not scale” warning

Many plans carry a note such as “Do not scale from this drawing”, because photocopying, printing on a different paper size or PDF “fit to page” settings change the size. Use written dimensions where they exist, and use a scale bar printed on the drawing to check: if the 5 m scale bar measures exactly 5 cm at 1:100, the print is true to scale.

Printing a true-size ruler

1. In the print dialog, choose Actual size or 100% — never “Fit to page”.
2. Print the ruler page from the pack.
3. Check it against a real ruler or a bank card (85.6 mm).
4. If it’s slightly off, your printer may be scaling; adjust the scale setting until the check bar matches.
5. Print on card stock or laminate for a sturdier ruler.

Other things to calibrate with

The card method is easiest because almost everyone has one and its width is standardised worldwide. Cover the number with your thumb if you prefer — only the edges matter.

Accuracy

A carefully calibrated screen ruler is usually accurate to within about half a millimetre over a card’s width, which is fine for quick checks, ring and bead sizes, or reading plans. For woodworking, sewing patterns or engineering, use a physical ruler or tape.

Scale ruler pack

The optional pack includes printable true-size rulers in centimetres and inches, architect scale strips (1/8, 1/4, 1/2 and 1 inch = 1 foot), metric scale strips (1:20, 1:50, 1:100, 1:200), a map scale bar sheet and a calibration check page. The on-screen ruler is free.

AI-assisted content

This page was drafted with AI assistance and reviewed before publishing.