Download.com (former ZDNet) 5-Star editors' pick: "It's an easy to use, well-designed and useful tool especially for engineering purposes..."
I have longed to get a free math expression evaluator for my engineering purposes: I used to do calculations like "a*x^3+b*x^2+c*x+d" or "ATN{(a-b)/(c-d)}" and change one of variables. It was something like "ATN{(5.783E+05-1.345E+05)/(3.255E-03-2.288E-03)}" and "3.255E-03" to be replaced with other values for instance. I have intensively searched the web in vain, so I wrote this program by myself. It is small enough in size not to hinder other windows and always visible while doing other tasks.
ExCalc accepts up to three variables as X, Y and Z. It's quite easy to get the solution of the two-dimensional equation for example. As the math expression and result change, the length or height automatically grows or shrinks.
You can freely customize its appearance as well as type, size and color of fonts.
29 engineering functions can be pasted from the Function Paster menu to the Expression Input box in a moment.
This program works under Windows Vista and earlier, 7, 8, 8.1 and 10 with no modification to Windows.