Probably the best way to determine the actual draw of the bow is to draw it with an extra long arrow. Have a friend (??) mark the arrow at the point where it is flush with the front of the bow at the shelf. Measure this and see what you get, Never, ever take what' s on the limb tag for granted. Most bows are actually as much as 1" longer than marked.
Now for determining your draw let me ask you this. How tall are you? Divide your height by 2.5 and you" ll have a pretty close estimate of what you should be drawing.