Draw Length is the distance from the nock point to the throat of the grip plus 1 3/4". Typically, this length will also be about the same length of arrow needed by the compound archer.
To measure your draw length, stand with your back to a wall stretching your arms out against the wall. Measure the distance from the end of your middle finger to the end of your other middle finger, basically the length of both arms, hands and chest. This measurement, minus 15 then divided by 2, is your draw length.
