The need to calculate the amount per square foot often arises in business and in everyday life. Building contractors need to know the cost per square foot to estimate total material costs and labor costs. When renting an apartment, the ability to calculate the amount per square foot allows you to determine if you’re paying too much.

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The area that your project might not always be rectangular in shape. For these cases, subdivide the area into smaller rectangles and then use the rectangle area formula to calculate each rectangle. Then total the area of all the rectangles.

For irregular shapes that have curves, consider subdividing the shape with rectangles that are small enough in size so that the irregular shape is completely filled with rectangles.

Consider any hidden costs. For the above example you might consider the costs associated with driving to the store to pick up the paint or the need to sand the wall. Consider that driving to the store includes labor costs for the driver and material costs for the gasoline and depreciation on the car.

Calculate the area of the project. First determine or measure the dimensions for the project involved. Consider the dimensions of your project. Use a rectangular wall for this example that has a width of 5 feet and a height of 10 feet.

Now use the area formula for a rectangle to calculate the square footage. The area of a rectangle is equal to its width multiplied by its length. In this example, the wall is 50 square feet, since 5 multiplied by 10 is 50.

Calculate the costs of the materials for the project. In the example, assume a half-gallon of paint is needed to paint the 5-foot by 10-foot wall. Assume the paint costs $20 per gallon. The total material costs to paint the wall are $10, since 0.5 multiplied by 20 is 10.

Calculate the cost of labor for the project. In the example, assume $20 per hour as the hourly labor rate for the painter. Assume the painter will take 1.5 hours to paint the wall. The labor cost to paint the wall is $35, since 1.5 times 20 is 35.

Calculate the total costs for the project. Add the total material and labors costs. In the example, the total material and labor costs for the painting the wall is $45, since $10, the cost for the materials, plus $35, the cost of labor, is $45.

Calculate the amount per square foot. Divide the total costs by the total area. In the example, the amount per square foot of the project is $0.90, since $45, the total costs for the project, divided by 50 square feet, the area of the project, is 90 cents per square foot.

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- cadre rectangles image by ninice64 from Fotolia.com