Word+Equate is an add-in for Microsoft Word. It lets you create live calculations directly in your Word document. Change a value and all subsequent calculations are immediately updated. Units are handled automatically and you can convert between units in the one calculation. Formatting supports subscripts, Greek variable names and mathematical symbols. All calculations steps are visible in the final document.
View the tutorial to better understand how to build you own calculations. Download to try Word+Equate for yourself.