Digital Ruler

Drag handles and coordinate system to measure

Coordinate System

Second Ruler

Dark

Red

45.0 mm

Distance

0.0°

Angle to X-axis

0.0°

How to Use

Drag the larger green handle to move the coordinate system independently
Drag the round handles at the line's ends to position the ruler (start point follows coordinate origin)
The ruler angle relative to the X-axis is displayed in green
Enable "Second Ruler" to measure angles between two lines; its end handle is amber
Use "Calibrate" for accurate measurements

Calibrate once

Screens differ in how many pixels they fit into a millimeter, and a browser does not tell. Until calibrated, the ruler assumes the web's standard of 96 pixels to the inch. For real millimeters, lay a ruler or a card on the screen, match the line to it and enter its length under Calibrate. A credit card is 85.6 mm wide.

Angles

The angle shows the line's direction against the X axis of the coordinate system, which you can move. With the second ruler on, the angle between the two lines appears at their common start.