Things You'll Need
Always measure and calculate TWICE.
When figuring a job for construction, a few formulas will help you complete a successful project. With a little practice, you will be an ace at building material calculations.
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Calculate the concrete. Most building projects that begin from the ground up must start with concrete. Multiply the length by width by height of the base, then divide that number by 27. This will tell you the needed concrete in cubic yards.
Calculate the 2-by-4 lumber for framing walls. Convert the entire length of the wall being constructed into inches (feet multiplied by 12). Now, divide the length in inches by 16. This will give you the number of 2-by-4s needed for one wall.
Calculate wall sheathing. Multiply the length of the wall by height to get the square feet of the wall surface. Since most sheathing (plywood, drywall, paneling) comes in 4-by-8-foot sheets, take the square feet of one sheet (32) and use it to divide the square feet of the wall. This will equal the number of 4-by-8 sheets to cover the wall.
Calculate framing and decking for a roof. Divide the entire length of the roof by 2 feet to find out how many rafters you'll need to frame the roof. For the decking, multiply the length by the width of the roof, convert to inches and divide by 32, the square feet of one sheet of plywood. This will equal the number of plywood sheets you'll need.
Calculate shingles or other roofing material. Three bundles of shingles equal one square of shingles. One square of shingles equals 100 square feet. So multiply the length by the width of the roof and divide that number by 100. This will give you the amount of material in squares needed for roofing. To convert into bundles, multiply that number by three.