Use a tape measure and round to the nearest 1/8”

List width first and length second (i.e. 40” x 80” = 40” wide x 80” long)

Measure the width
Measure window width (including molding or trim, if you want to cover them)
- Add at least another 4" to each side
-Multiply by 2 or 3 for fullness, depending on fabric
-The final measurement is the total width needed

Measure the length There are several ways to measure the length of the window depending on your preference for how far the curtains will extend.