CHILP82 So much easier than the dashboard calculator!
Always available when you need it. A keystroke to bring it up and then type in the calculations you need done (as opposed to the dashboard - keystroke, wait, use the mouse to make sure calculator is selected, then use the keyboard or mouse to type the calculation in).
It can also do a few more advanced calculations (trig, logs, square roots etc).
And it's free!
(Version 1.4.2)