Calc! for

From Daniel Dube:

Powerful calculator and unit conversion utility featuring four modes of operation: standard, unit conversion, programmer, statistics.

Using Calc! is as easy as using your favorite Texas Instruments or Casio calculator. With Calc! you can enter the whole expression, including brackets, functions and operators (for example, ((9*8) - 7 + 34.23). You can always return to expression you calculated before, change it and recalculate it.

Calc! can quickly and easily convert more than 100 different units in 11 categories, and users can define new ones. The categories include angle, area, energy, length, power, pressure, speed, temperature, time / frequency, volume and force&weight.