Remove the patio cushions from the chairs.
Use a measuring tape to measure the width and height of the cushion front and back. Add four inches to the measurements to allow for the seams and to ensure enough fabric. Multiply by the number of identical cushions. Write down all of the measurements.
Add each of the measurements together with a calculator. Take the total number and divide it by 36 to get the required yardage.
Round up the total number and add an extra half yard. Plan on extra yardage if you want to make pillows or keep some fabric on hand for tear repair.
Visit your local fabric store. Choose from outdoor fabric that has been treated to withstand moisture.