GNU Units

With this program you enter in the units that you have and the units that you want to convert to, and the program tells you what to multiply by or divide by to get there.

You have: furlongs per fortnight
You want: mph
* 0.00037202455
/ 2687.9946

You have: kilowatt hours
You want: calories
* 859845.23
/ 1.163e-06