You can do it at home by looking up the weight of your arrow per inch. Multiply the weight per inch by the total length of you arrow. 4 inch vains are about 10-15 grains each. Nocks are around 15 grains and I believe inserts are around 20 grains. Thats will give you in the ball park for your arrow weight.

My arrows weigh in at 395 grains including broadhead.