How long should a bowstring be as it relates to the length of the bow?

Question

I have a 72 inch longbow (a little less when strung) and I need a new string, but websites only say the string length and not the length of bow that it fits. How long a string should I buy?

Answer 1

Rule of thumb is bow length minus 3.  But depending on riser design, this can vary by around 1/4" or so.

If you have the old string, best thing to do is take that string untwist is fully and measure it.

Answer 2

Measure the un-braced bow between the nocks (the string should not be on the bow); this is the "length" of the bow. Now subtract 3 or 4 inches from this; this is called the "AMO length" and will be the ***approximate*** length of the string. AMO is the "Archery Manufacturer's Organization", and AMO bow/string lengths are standardized for convenience/ease of use; an "AMO 72 inch" longbow (it will be marked as AMO 72") generally needs a 68 or 69 inch string.

Since every general "rule of thumb" has an exception, you may need a shorter -- or longer -- string for your bow. If you purchased your bow from a company (or custom bowyer) that has a website, look for the information you need there; I remember a custom "72-inch" longbow with a specific design which required a string 66 inches long (6 inches shorter than the nock-to-nock measurement).

It really depends a lot on the design of the bow, and the optimum brace-height of the bow, as well as how much "stretch" the string has. So, yeah, check with whoever made the bow if you can; if you can't, well, the AMO length is a good starting point.