No tape measure at hand?
Measure mm/cm & inches online in real size
With lineal-online.de, your screen becomes a measuring tool!
You can measure directly on your monitor in millimeters/centimeters and inches — calibrated, no registration, and completely free. With a simple manual calibration, you can verify the scale using a real-sized bank card.
How calibration works
- Drag the dashed blue box to match the width of a bank card (85.6 mm).
- Alternatively, enter any known length (also in inches).
- The scaling is stored locally. If you zoom or change monitors, recalibration may be required.
Frequently Asked Questions
How do I measure with the online ruler in cm and inches?
Select the unit at the top (mm/cm or inch) and calibrate once using a bank card (85.6 mm). The ruler will then display in true physical size.
Is it really accurate?
Yes. We use a measured px/mm factor. Calibration lets you verify and fine-tune accuracy.
What’s the difference between a ruler, a measuring tape, and a folding rule?
A ruler measures short lengths (e.g., 30 cm), a measuring tape uses the metric scale, and a folding rule extends up to several meters.
Our online ruler displays both cm/mm and inches.
Does the online ruler work on mobile?
Yes. On narrow displays, calibrate vertically. Recalibrate after zooming or switching monitors.
Calibration
Drag the blue box below until it matches the exact width of a bank card (85.6 mm). Alternatively, enter a known length.