I'd just like to inform you about a piece of freeware called "convert" by Josh Madison. This is an amazingly useful program - something that every mechanical engineer should have in my opinion! It's function is simple - it converts any unit of measure. Force, mass, volume, acceleration, density, distance etc. Here's a screenshot: You can download "convert" from the following location: http://joshmadison.com/software/convert-for-windows/ I've had this incredibly useful, unobtrusive program sitting on my PC desktop for years. I hope that you will find it as indispensable as I do!
Another similar tool that I like is ConvertAll. http://convertall.bellz.org/index.html It is easier for me to find the units I'm looking for, because I can just type the unit. With convert, I have to figure out which of the seventeen tabs the quantity in question falls under, and then find the specific "to" and "from" units in the lists.