If you are wondering how you can calculate the number of lights you need to decorate a Christmas tree or house for Christmas, we share the tips and guidelines below.
Christmas trees, roofs, and pretty much any other item you can decorate with Christmas lights come in various sizes. Similarly, Christmas lights come in various sizes. So, when decorating your Christmas tree or any other thing with string lights, there could be size incompatibility.
What does this mean? Well, it means your light strings can either be too long or too short for decorating Christmas trees or any other item you intend to decorate. But then, if you knew beforehand how many lights you would need, you could avoid a situation where you have to shorten or extend your light strands.
How to Determine How Many Lights You Need for a Christmas Tree
When trying to figure out how many lights you need for indoor Christmas trees, you do not really need to calculate. You can get a quick estimate using:
- The lighting brightness you want
- The height of the tree.
- The number of bulbs in one strand of your Christmas lights
A general rule of thumb for making out the number of Christmas lights you need for your indoor tree is one strand per vertical foot of the tree. In other words, if your tree is one ft. tall, you need a strand of light string. If the tree is 5 feet, you need 5 strands.
The number of bulbs on each strand comes into play when you are deciding how bright you want your tree to be. Typically, incandescent lights come with 100-200 bulbs per strand. If you want a very bright decoration, you should opt for a light string with 200 incandescent bulbs per strand. If you want something that is just right, a string with 150 bulbs per strand would do.
But if you do not want something that is too bright, 100 bulbs per strand should be okay.
While the estimate above is usually helpful, you could buy 1-2 extra strands. This will come in handy if your estimate offers fewer lights than you need.
Outdoor Trees (Deciduous Trees)
When trying to figure out the number of lights needed to decorate your outdoor Christmas tree, the following variables matter:
- The height of the tree
- The circumference of the tree trunk
- The length of the branches
- The circumference of the branches
- Bulb spacing
We explain how they matter using the example below.
For instance, if your Christmas tree is 5 feet tall with a circumference of 1 foot, and your Christmas lights have a bulb spacing of 2 inches, you can calculate how many lights you need as follows:
Before you go into the calculations, convert all the values to inches:
Height of the tree – 5 feet = 60 inches
Circumference of the tree – 1 feet = 12 inches
Bulb spacing = 2 inches
= (60 x 12) ÷ 2
720 ÷ 2
= 360 inches.
For the tree in the instance above, you need around 360 inches (30 feet) of light strings.
For the same tree and lights, if you intend to decorate six of the branches, and each branch is 2 feet long with a circumference of 5 inches, calculate the length of lights you need for the branches like this:
First, convert the length of the branch to inches:
Length of each branch – 2 feet = 24 inches.
Branch length = 24 inches
Branch circumference = 5 inches
Bulb spacing = 2 inches
Length of lights you need for each branch = (24 x 5) ÷ 2
= 120 ÷ 2
= 60 inches.
For each branch, you need 60 inches (5 feet) of Christmas lights for each branch. So, for all 6 branches, you need 30 feet (6 x 5 feet) of light strings.
If you need 30 feet for 6 branches and 30 feet for the tree trunk itself, in total, you will need 60 feet of light strings for the tree in the example.
Quick Estimation for Outdoor Trees
If you would rather work with a quick estimate for your outdoor trees, the following rules of thumb should come in handy:
- For trees 10 feet tall or lower, you need around 30 to 40 mini lights per ft.
- For trees taller than 10 feet, you need around 50 to 55 mini lights per foot.
- For trees shorter than 10 feet, you need around 6 to 12 C7 lights per foot.
- For trees between 10 and 30 feet tall, you need around 15 to 20 C7 lights per foot.
- For trees over 30 feet tall, you need around 25 C7 lights per foot.
C9 lights are usually reserved for trees measuring 15 feet or taller.
- For trees between 15 and 30 feet tall, you need around 15 to 20 C9 lights per foot.
- For trees over 30 feet tall, you need around 25 C9 lights per foot.
As we said for the indoor tree estimates, you can always get 1-2 extra stands in case your estimate comes with fewer lights than you need.
Roof and Window
Calculating how many lights you need for your roof is real simple. Once you know the total length you want to cover, the rest is easy.
For instance, if you intend to cover a total distance of 100 feet while leaving 4 inches of space between each bulb, you can calculate the number of bulbs you need as follows:
First, convert the total distance to inches:
Total distance to cover – 100 feet = 1200 inches.
Bulb spacing = 4 inches.
Number of bulbs needed = 1200/4 = 300 bulbs.
Bushes and Hedges
When decorating shrubs and hedges, most people opt for net lights, and rightly so. Net lights are easy to use; you can readily lay them out on the shrubs.
To calculate the number of Christmas net lights, you need:
- Calculate the area of single net light.
- Get the area you want to cover per bush.
- Then divide the area of the bush by the area of a single net light.
For instance, if the surface area of a single bush is 75 square feet and a net light is 3 feet long and 2.5 feet wide, you can get the number of nets you need like this:
First, calculate the area of a net light:
Area of net light = 3 x 2.5 = 7.5 square feet
surface area of the bush = 75 square feet
area of a net light = 7.5 square feet
number of nets needed = 75 ÷ 7.5 = 10 net lights.
If you do not know the surface area of your hedges, you can estimate that using their shape. In other words, if your bush is shaped like a cuboid, you can get the surface area of your bush using the formula for the surface area of a cuboid. If it is shaped like a cone, you can get the surface area using the formula for the surface area of a cone.
NOTE: When estimating, if you end up with a decimal number, round that number up to the nearest whole number. For instance, if your estimated value is 10.2, 10.5, or 10.6, approximate to 11. It is better to end up with an extra strand than to be short by a few strands.