To calculate the number of panels you would need to order for your project, choose the length based on the height of your wall. The panels are 24 inches wide, so divide the width of your wall by 24 inches to calculate the number of panels your wall would require. Round up to the nearest whole number. For example, if your wall is 112 inches wide, divide by 24, which equals 4.66. Round up to the nearest whole number (5), which means you need 5 panels.