There is some confusion when referring to the length of a bowstring. Length can be ascertained in two ways; Actual and AMO.
AMO length refers to the length of a bow as standardized by the Archery Manufacturers and Merchants Organization (AMO). The AMO is an industry trade organization that sets standards for archery equipment, including the measurement of bow length.
But because bows (riser and limbs) are essentially curved and the string is straight, the two are not the same length. Typically a recurve string is 4″ shorter than the bow, and a longbow string is around 3″ shorter than the bow.
So for example, a 66″ recurve bow requires a 66″ AMO string, but the ACTUAL length of the string will be 62″ (4″ less). Similarly, a 72″ longbow requires a 72″ AMO string, but that means the ACTUAL length is 69″ (3″ less).
When ordering a custom bowstring it is very important to understand the difference between AMO and ACTUAL length.
If you are replacing an existing string, it is recommended that you hook it onto a nail, draw the string as tight as possible, and using a measuring tape measure from end to end (including the end loops). This is your ACTUAL length.
Here is an AMO chart showing the AMO and string length for both RECURVE and LONGBOW. Note that recurve string length is typically 4″ less than a bow’s AMO length, and longbow string length is typically 3″ less than the longbow’s AMO length. However not all bows are consistent with AMO and therefore it is HIGHLY RECOMMENDED that you use the “nail and tape measure” method to measure your string’s ACTUAL length.
