How to Measure How Far a Yard of Concrete Will Spread
Whether your project is a new concrete sidewalk, carport slab or patio, you will have to estimate how much concrete you will need to fill the forms. Commercial retail ready-mixed concrete is ordered and sold by the cubic yard, and defining the volume of your project area will help you calculate how much concrete you will need for your project. The formula used to determine how far a yard of concrete will spread is based on the overall average thickness of the area to be covered. Does this Spark an idea?
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Instructions
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Determine the desired finished thickness of the concrete mass. Typically, concrete slabs for sidewalks or patios are 4 inches thick for all common applications. Concrete footings or column bases can vary from 8 to 12 inches thick, depending on site requirements. If the area to be poured varies in thickness, take a number of measurements and average them.
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Convert the concrete thickness to a decimal equivalent. For example, if the concrete slab is to be 4 inches thick, divide 12 inches by 4 inches to equal 3, then divide 1 (foot) by 3 to equal .333 or 1/3 of a linear foot.
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Divide the cubic feet in a cubic yard of concrete by the average thickness decimal to determine the area in square feet that will be covered. There are 27 cubic feet in a cubic yard divided by .333 (4 inches) equals approximately 81.1-square feet of area the cubic yard will cover.
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Tips & Warnings
The basic formula for calculating the concrete needed for a project is to measure the overall length times the overall width times the average depth of the slab area to define the volume of the slab or footing area in cubic feet. The total is then divided by 27 to determine the cubic yards of concrete needed.
