There are a few different ways that you can measure the size of your deck. The most common way is to measure the length and width of the deck in feet. You can also measure the area of the deck in square feet by multiplying the length and width together. Another way to measure the size of your deck is to use the square footage method. This method uses the length and width of your deck in inches, multiplied by 12, to determine how many square feet your deck has.