A string of Christmas lights can range in length from a few feet to hundreds of feet, depending on the size of the area you want to illuminate. The most common length of a standard Christmas light string is between 15 and 25 feet. However, some lights can be longer or shorter, depending on the type of lighting and the purpose of the light display. For example, a string of 100 lights may be used to decorate a small tree or a wreath, while a string of 1000 lights may be used to light up an entire yard or house.