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Ruler Tool

Welcome to the Ruler Tool Help documentation. This is the on-line help file that accompanies the Ruler Tool software. You can use the menu below or displayed on the left of this page to navigate.


The Ruler Tool is a great little utility for accurately measuring anything on your computer screen. This includes images, font heights, dialog boxes, etc. This can be very useful for web work and graphic design - allowing you to avoid having to screen-grab and view in an image manipulation package.

Ruler Tool Screenshot
Ruler Tool Screenshot

The ability to make the ruler semi-transparent and then drag a line or region exactly over the area you are interested in makes lining things up extremely easy and accurate. Moreover, you can set your own custom scales and even reverse and rotate the whole ruler. Best of all, it is completely free.

Example of a semi-transparent ruler.
You can make your ruler semi-transparent to more accurately line up edges.

Recording Screen Measurements

Step 1

To make a screen measurement, first line up any part of the Ruler Tool over the image or screen area you wish to measure, as shown above. You can use any part of the ruler for a measurement, you do not have to start with the zero end.

Step 2

Next click and drag with the left mouse button to move the start line such that it lines up with one side of the image. This is a vertical XORed line that runs the full height or width of the ruler.

Dragging with the control key displays the measurement region.
Dragging with the control key displays the measurement region.

Step 3

Now hold down the Control key and drag the left mouse button to extend the measurement region over the extent of the image. As shown in the image above, you can read off the measured size from the area highlighted. You will see the value update as you drag.

Measurement region extended to full width of underlying image
Measurement region extended to full width of underlying image

Use the keyboard and mouse wheel also to adjust the measurement area.

Mouse and Keyboard Shortcuts

You can also use the mouse wheel and/or the Arrow keys to move the measurement area. The Up and Left keys decrement the current position whilst the Down and Right keys Increment it.

In both cases the Control key allows you to adjust the end-point of the measurement region in exactly the same way as when dragging with the mouse. Also, holding down the Shift key increases the increment/decrement to 10 pixel, allowing you to move around much faster.

Moving and Resizing the Ruler

You can move the ruler any time by simply clicking and dragging it with the right mouse button. You can also use the Alt + Arrow keys to nudge the window around. When doing so, holding down the Shift key increases the nudge increment to 10 pixels instead of 1.

You can resize the rule by simple moving the mouse over either end util you see the resize mouse cursor. Then simply clik and drag the end with the left mouse button.

Resizing can be done from either edge.
Resizing can be done from either edge.

Display Options

Ruler Tool menu

Clicking and releasing the right mouse button anywhere within the ruler displays its context menu. This contains all the ruler's display options as well as some basic settings.

This includes being able to re-orient both the scale and the rotation of the ruler.

Left to Right
Right to Left
Top to Bottom
Bottom to Top

Ruler Tool in vertical format

These items change either the direction of the scale or the orientation of the ruler. The image to the left shows it in Top to Bottom orientation running vertically down the page.

Always on Top

Keeps the ruler on top of all other open windows regardless of which window you are currently working in.

Snap to Edges

Snaps the ruler to the closest screen edge as you drag it close. This way you can ensure the ruler starts and/or finishes at exactly the edge of the screen.

Ruler Opacity

Select one of these sub-menu items to increase or decrease the level of transparency. This feature is only available in Windows 2000 and above (including Windows XP). Setting the opacity to 100% means that the ruler cannot be seen through whilst 25% make the ruler barely visible. 75% is usually the best compromise.


Displays the Ruler Settings dialog described in the next section.

Ruler Settings

Ruler Tool vertical format

The Ruler Tool allows you to adjust the displayed measurement value by applying a scaling factor. This can be used to display Points, Picas and a wide range of values derived from the screen co-ordinates.

Proposed New Features

The following are some temporary notes for future developments - I will move these into the Ruler Tool project when I create it.

  • Able to rotate the ruler to an arbitraty angle using a special rotation node.
  • Have a small screen magnification area that follows the mouse when dragging to allow better alignment.
  • Display both pixels and the scaled units together.
  • Able to display both a vertical and horizontal ruler together and find co-ordinates of points within them.


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