Scale length is a measurement of the bass. Most basses are about 30" (short), 32" (medium), 34" (long) or 35" and up (extra long).
String length is a measurement of the string. We list the usable winding length: from the ball end to where the full winding stops and the taper or silk begins. That part has to reach past the nut so only full winding sits on the nut and saddle.
Because the string also has to travel through the bridge, and through the body on string-through basses, the string is always longer than the scale. A 34" bass usually takes long scale strings at about 37.25"; a 35" bass often takes extra long at about 38".
How to measure your bass · Bass string length guide · Shop long scale sets · Shop extra long sets