It's not 100% on the mark, Doug, because the calculator uses average weights for arrow components. If the inserts, vanes and nocks weigh more or less than the averages the program uses, it will not weigh out dead nuts the same as the calculator says. On the other hand, it's plenty close enough to give you a very good idea of what you'll wind up with.

Actually, I've never had it be off more than 5 grains with the arrows I've run on it. I've seen greater weight variances than that within a dozen carbon shafts.

Agreed on the recommendation for cut on contact heads. Steelforce, Magnus Stingers, etc.