In science and math, we often convert a number or quantity with a dimensional unit to a different unit, like meters to kilometers. Dimensional Analysis (also called Factor-Label Method or the Unit Factor Method) is a problem-solving method that uses the fact that any number or expression can be multiplied by one without changing its value. This allows us to convert from one unit to another using something called a conversion factor. Remember, the actual quantity does not change, only the unit, and the unit is just a standard reference that we are usually pretty familiar with (or should be familiar with).