Christmas Lights Calculator

How many lights does a Christmas tree need?

The standard guide is 100 lights for every foot of tree height, which gives the full, even glow most people picture. A 7 foot tree therefore takes about 700 lights. Choose the light setting, at 70 per foot, for a sparser and more traditional look where the lights are accents rather than the main event. Choose heavy, at 150 per foot, for a dense, sparkling tree of the kind used in shop windows and hotel lobbies.

Height is the right measure to start from because a taller tree is also wider and deeper, so the surface area you are covering grows faster than the height alone suggests. If your tree is unusually slim or unusually full for its height, adjust one step: pick the lighter setting for a pencil tree and the heavier one for a very full traditional fir.

Wrapping the tree properly

Most people wrap lights around the outside like a ribbon, which leaves the tree looking flat once the ornaments go on. The method decorators use is to work vertically, section by section. Start at the trunk near the base and run the string out along a branch to the tip, then back in toward the trunk, then out along the next branch. Work up one vertical section at a time until you reach the top, then move around the tree and repeat.

It takes longer, but it puts light deep inside the tree as well as on the surface, which is what creates the sense of depth. Start at the top if your only outlet is above, or at the bottom if the plug is at floor level, and check the string works before it goes anywhere near the branches.

Safety and practical notes

• Respect the connection limit. Traditional incandescent sets usually allow only three end to end. LED sets often allow many more, but always check the box rather than assuming.
• Use the right lights for the place. Only lights rated for outdoor use should go outside, and outdoor circuits should be protected by a residual current device or GFCI outlet.
• Inspect old sets. Cracked insulation, loose bulbs and scorched sockets mean it is time to replace the set rather than repair it.
• Choose LEDs for a big tree. They use a fraction of the power, stay cool to the touch, and let you run far more of them from one outlet.
• Switch them off overnight. A timer plug makes this automatic and cuts the running cost.

Buying lights in the sales? The Black Friday discount calculator works out what a discounted set plus a coupon actually costs, and the Christmas countdown tells you how long you have before the tree needs to be up.