scale for weighing yarn

[jberry16]

I'm thinking of buying a scale to weigh my yarns so I know how much is left in a skein after a project, do any of you have one if so what kind do you have? I was looking at this one from Linens 'n Things. What's your opinion? Also do you know roughly how to determine how many yards is in so many oz of a skein, for different weights of yarn (fingering, ww, etc.)?