Electric Bass Single Strings
Electric basses come in different scale lengths, as well as different lengths based on how the ball end of the string mounts in the bridge.
Here's the scale length guide:
Standard Scale: 34" nut to bridge saddle
Long Scale: 35" nut to bridge saddle
XL Scale: 38" nut to bridge saddle
The above lengths assume the ball end of the string anchors in the bridge, on top of the body. If the string goes through the body and the ball seats on back of the body, add 2" to the string length. When in doubt, measure nut to saddle (that give you the scale length), and then remove an old string and get the overall length.