Many people like the look of pinch pleat curtains. The pinch pleats at the top of the curtain create a full and formal look to the drapes. You can sew pinch pleat curtains in a relatively short period of time, especially if you plan well beforehand. Part of that planning, and probably the most important, is calculating how much fabric you need to purchase. Adding pleats to your curtains or drapes also adds to the amount of fabric you need. Take some careful measurements at the beginning and make your project go smoothly.
Measure across the width of the window. Make sure to measure from the outside edge of the window casing to the other outside edge of the window casing and not just the glass. Write down that measurement.
Add 4 inches to your window measurement so that the two panels of the pleated curtains overlap in the center when you close them.
Figure out how many pleats you want to add to your curtains. Divide the window width by six or eight. Plan on a pleat every 6 to 8 inches, depending on the width of your windows.
Add 4 inches for each double pinch pleat. Add another 2 inches for each fold you desire in the pleat. If you want 10 double pinch pleats you will add 40 inches to the width measurement. If you want 10 triple pleats you will add 60 inches.
Use your figured measurements to know how wide the fabric should be you need to buy for each panel. Remember, you will need two drapery panels for each window. Sew two lengths of fabric together if necessary to get the needed width before beginning to sew your pleats.
Measure the length of the window as far down as you want the curtains to hang. Add 4 inches to allow for top and bottom hems. Use this measurement to figure out how many yards of total fabric you need.