Page ruler to get the pixel width and height of any elements and to measure distances
Web Ruler allows:
• View the width, height and top, bottom, left and right position of your measurements
• Use the arrows on the keyboard to per-pixelly change the position of the measuring field, or its size
• Easily change the size of the measuring field by drag it by the edges
• In the panel it is possible to set all parameters manually
• Set the position of the panel at the top or bottom of the page
• Special "Element Mode" allows you to very simply measure a page element by hovering the mouse over it
• Navigate through parents, children and sibling elements of any measured element
• Displays guides from the edges of the ruler

Please Note: To use Web Ruler on local pages you will need to enable the "Allow access to file URLs" option on the Extensions Manage page
Web Ruler - Chrome Extension