what is the formula for calculating the amount of decking needed
2[(12W + d)/(x + d)][(12L + j)/j], and compute the number of screws needed for the frame of the deck with the formula. 4(12L +j)/j. Add the two numbers that you get, and this is the approximate number of screws you will need for the entire deck.You may want to factor in an extra 3%.ext, use the following equation to calculate the total length of deck boards needed to construct the top of the deck, L(12W-x)/(x + d) + L. You can use the simplified form, (12WL + dL)/(x + d). Add up the two numbers found in Steps 3 and 4, and this is the total length of board needed to construct the deck.