I wrote this equation because I think that the equation developed by Sheffield University for the length of Christmas lights needed for the perfect Christmas tree  way underestimates the actual amount. According to Lowe's a good rule of thumb is about 65 lightbulbs per foot of the tree's height.
See  Lowe's Christmas Tree Decorating.

 Your typical string of Christmas lights has about 3-4 inches between each light bulb. This equation calculates the number of lights needed for your  tree given the height of your tree, the number of lights you want per foot of height, and the distance between each light bulb.

Approximate number of lights needed for common tree heights

See also

• University of Sheffield Christmas Tree lights

External Links

• University of Sheffield Christmas Tree Equations