Measure the width that you want for your awning. Keep in mind that downspouts and light fixtures may be in the way. Take care to measure in an area that has a clear span without obstructions. Most window awnings should be mounted six to 12 inches above a window, according to the Sunshine Awning Company website. Patio awnings should allow six to 12 inches above any existing doors.
Write down your measurements as you take them on a sheet of paper.
Add extra inches to your window measurements to allow for frames that pop out from the wall. You can mount the awnings directly next to the window frames or wider than the frames by up to 12 inches on either side for the best look.
Use the tape measure or yardstick to calculate how much projection is necessary for your deck or patio awning. This is particularly important if you want it to cover a barbecue grill or patio table effectively. Some people like for their patio or deck awnings to extend beyond the wood or concrete area so that many people can sit under it comfortably without feeling raindrops or the heat from the sun.
Take the measurements with you to shop for an awning.