ScaleCalculator

Scale Ruler

Calibrate to your screen, choose a scale, and measure drawings on screen in real-world units.

On-screen scale ruler

Calibrate to your screen, pick a scale, then measure a drawing on screen.

Match this box to a real credit card (85.6 mm wide)

Hold a bank/credit card against the dashed box and drag the Calibration slider until they match — now the ruler is true-to-life on your screen. The blue numbers show the real-world size at the chosen scale.

How to use the scale ruler

  1. Calibrate. Hold a credit card against the dashed box and drag the slider until they’re the same width — this makes the ruler true-to-life on your display.
  2. Pick the scale. Choose the scale your drawing or map is drawn at (1:50, 1:100, etc.).
  3. Measure. Hold the drawing against the on-screen ruler; the blue labels read off the real-world size.

Prefer numbers?

Use the scale calculator to convert any measurement exactly, the scale conversion chart for a printable lookup table, or the architectural scale calculator for architect and engineer scales.

Frequently asked questions

How does an on-screen scale ruler work?

First calibrate it to your monitor by matching the on-screen box to a real credit card. Then pick your drawing’s scale — the ruler’s blue labels show the real-world distance for whatever you measure on screen.

How do I read a 1:50 scale ruler?

At 1:50, every 1 cm on the ruler represents 50 cm (0.5 m) in real life. So a line that measures 8 cm on a 1:50 drawing is 4 m in reality.

Can I print a scale ruler?

Yes — use your browser’s print option and set the printer to 100% (not "fit to page") so distances stay accurate. For a quick lookup, the scale conversion chart is also print-friendly.