Pixel Ruler is a free application that claims to allow you to use your mouse to dynamically measure pixels. With it, you can accurately measure selected onscreen views in pixels, which can help when configuring image formats, creating graphics, and scaling images. It shows measurements in pixels up to 2,500 pixels in width or 1,500 pixels in height.
After a painless download and a surprisingly detailed installation process, a horizontal ruler appeared on our screen. There's also a ruler for vertical measurement. The interface consists only of these rulers; there are no navigation buttons or other controls. We would have consulted a Help file, but alas, none exists. However, this tool is extremely easy to use. Pixel Ruler floats above the desktop and can be dragged and dropped anywhere on the screen. As we moved our cursor up and down the ruler, a tiny box displayed the measurement from the end point in pixels. Clicking or double-clicking the ruler switches between the horizontal and vertical views. Right-clicking a ruler closes the program.
This application installs and uninstalls cleanly. Pixel Ruler doesn't require personal information or registration, nor does it ask for a username or password. As far as pixel measurement goes, surely there is a better option.