On-screen Ruler is a classic app initially designed to help people with computers, usability, and the software development process.

On-screen Ruler looks neat and is easy to use once you view the help on the official home page. Otherwise, you might find yourself just staring at a ruler. Shortcuts are the trick here. Our first test was to resize the ruler for measuring by double-clicking for automatic sizing, then resing to measure. You can see this in our third screenshot.

Functionality:
Align
Calibrate
Exit
Measure
Resize
Update

Options:
Color
Font
Language
Marker
Orientation
Snap
Shortcuts
Stay on top
Transparency
Units