How to Calculate Max Run for String Lights

For longer runs of string lights one must keep in mind the "max run" that a cord will safely allow. Use this handy calculator below to ensure your cord isn't overloaded.

Calculating Your Maximum Length of String Lights

Every string light cord has a specification listed as "max run." Based on the max run and the wattage of bulbs you want to use, this calculator gives you the maximum number of bulbs and length you can safely have based on the cord you select. Many string light cords can connect end-to-end, so this helps you know your maximum length. Additionally, the 330-foot bulk reels may not allow you to use the entire length if you choose bulbs that are higher wattage.

One thing to keep in mind ... be sure to check a cord's product specs of the maximum allowed wattage per socket. If you have any questions or need additional assistance, contact us through our live chat (bottom right corner), send us an email at