Pinch pleat curtains are an elegant home-decor accent, as the pleats in the fabric make the curtains look very full. For this reason, though, be very careful when measuring. The curtains use more fabric than you may expect, and buying the wrong size of pre-made curtains, or cutting the fabric incorrectly, is a waste of time and money. Taking careful measurements before buying the pre-made curtains -- or even before buying the fabric, if making your own curtains -- is a must.
Install your curtain rod before measuring the window, to give you a guide for measuring from the top of the window casing.
Place the measuring tape at the top of the curtain rod. Hold the end of the measuring tape there, while you pull the other end down to where you want your pinch pleat drapes to hang. Write this measurement down if you are planning to buy pre-made drapes.
Add 20 cm (8 inches) to the length measurement, to account for the rod casing and the bottom hem if you are going to sew your own pinch pleat drapes. Write this measurement down.
Measure across the width of the window. Measure from the outside edge of the window casing to the other outside edge of the window casing, and not just the glass. Write this measurement down for purchasing pre-made drapes. Double the window width for buying enough fabric, to account for the pinch pleats, allowing for one every 15 to 20 cm (6 or 8 inches) and the overlap of the two panels when closing the curtains. Write down these measurements.
Use a metal measuring tape that has the lip at the beginning end, especially when measuring from the curtain rod down the length of the window. This way, you do not need one person to hold it at the top for you. When measuring the width of the window, take into account the number of pleats you will need. Wider windows will take more pleats than narrow ones. If in doubt of how many pleats and how much fabric you need to make your own pinch pleat curtains, triple the fabric. Use any leftovers to make matching pillows.