All of our Classic Light Strings made for our C7 (E12) and C9 (E17) bulbs, regardless of socket count, have an 18 inch (~0.5 meter) length of wire from the plug to the first socket, called the lead. The sockets are spaced 12 inches (~0.3 meters) apart, and there’s another 12 inches of wire leading to the female plug on the end of the light string; this is called the tail.
We currently sell our C7 and C9 light strings in two lengths: 10-socket and 25-socket:
All 25-socket light strings thus have 25 feet of lighted length, and are 26.5 feet (~8 meters) total when accounting for the lead-in and tail.
All 10-socket light strings have 10 feet of lighted length and are 11.5 feet (~3.5 meters) total when accounting for the lead-in and tail.
When calculating how many lights you need for your tree or roofline, keep in mind that the lead-in and tail of interconnected sets will not be lit and thus you should use the lighted length of our light strings (not the total length) to calculate how many you might need.
This also means that interconnected sets will not maintain the the 12 inch spacing between the last bulb on one strand and the first bulb of the next. On a tree, you can simply tuck the extra wire into the tree where it can't be seen and no one will be the wiser, but if you're using them in a linear application, the extra wire may be more visible. If this is a concern to you, see our note on large installations.