HOW TO CALCULATE YOUR GARLAND LENGTH
Your garland needs to be as long as the top of your mantel.
If you want it to drape off the ends, add about 4' to your measurement so it can hang 2' off each side.
To swag across the front, it needs to be at least 1.5 times the top of your mantel.
To hang to the floor, measure the height of your mantel and multiply that by two. Add that measurement to how wide your mantel is.