A Ruler for Windows is an on-screen pixel ruler, that allows you to perform measurements on your screen. It comes with to skins that resemble a wood ruler and a transparent plastic ruler. You can customize the length of the ruler, use it vertical or horizontal, and even magnify the screen up to 4x for more accurate measurements. A Ruler for Windows only supports pixel units

A Ruler for Windows lets you layer one or more rulers on your screen at once.  As you can see through the clear plastic ruler you can even continue typing under it.

Special 2x, 3x, and 4x modes allow you to take a snapshot of your primary screen and magnify it to more easily measure between very fine points.

Ticks can be placed on which ever long edge you prefer. You can click near tick to have a measuring line automatically drawn at an exact location.

The ruler can be flipped horizontally or vertically, resized to an exact length or resized by dragging it to a desired length.