Would you believe scientists have figured out the formula for a perfectly decorated Christmas tree? They say multiply the height by three to get the amount of lights you will need. There’s more, read on. So, for a 6 foot tree, three times 72 is 216. Y0u would want 216 inches of lights or about 18 feet. As for the size of the star, divide the height by 10 and that’s how tall your star should be. So, for a 6 foot tree divide 72 inches by 10. You star is about 7 inches tall. Elementary, right?