I'm looking for a single word to describe the combination of a number and unit. For example, “6 watts” or “2.5 kilometers”. Measurement is the closest I’ve come, but sounds cumbersome. Does anyone know of a better word to express this idea?
The word you want is quantity.
You can often just use quantity. However, the term for a number which does not have a unit is dimensionless quantity, and the opposite term is dimensional quantity. So use dimensional quantity when it is important to make the distinction (and you don’t mind using a ten dollar word).¹
If OP wants to sound a bit technical, he could call them metrics - a set of measurements that quantify results.