The Windows calculator is a useful utility but not the most convenient to use or start, given that it is several levels down in the Start Menu.

Calq is a calculator that appears on a single keystroke. It may look simple but it has plenty of clever tricks.

Once installed it appears whenever F7 is pressed, and an icon in the Notification Area shows that it is running.

There are plenty of settings that can be changed, including where the Calq display appears on the Desktop. The level of transparency can be changed as well as how quickly it disappears if no keys are pressed. The keyboard shortcut used to start Calq can also be changed.

Frequent calculations can also be given a keyboard shortcut as well, a very useful touch that is much appreciated. By default Calq waits until Enter is pressed before making the calculation but it can be set to display results immediately.

This is a very useful utility, although some of the calculation capabilities can be found in the Launchy utility, which is more flexible.