Concrete is most often measured and sold by volume, specifically in cubic yards. To determine how much concrete you need, you'll typically calculate the volume of the area you intend to fill with concrete, and then convert that volume to cubic yards.
Here's a breakdown of the process:
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Calculate the Volume in Cubic Feet:
- First, determine the dimensions (length, width, and depth) of the area where the concrete will be placed. Make sure all dimensions are in feet.
- Multiply the length, width, and depth to get the volume in cubic feet.
Example: If you're pouring a slab that is 10 feet long, 10 feet wide, and 4 inches (0.333 feet) thick, the calculation is: 10 ft x 10 ft x 0.333 ft = 33.3 cubic feet.
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Convert Cubic Feet to Cubic Yards:
- Since concrete is usually sold by the cubic yard, you need to convert your result from cubic feet to cubic yards. There are 27 cubic feet in 1 cubic yard.
- Divide the total cubic feet by 27 to find the volume in cubic yards.
Example: Continuing from the previous example, 33.3 cubic feet / 27 cubic feet/cubic yard = 1.23 cubic yards.
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Account for Waste:
- It's always a good idea to order slightly more concrete than you calculate to account for spills, uneven ground, or other unforeseen circumstances. A general rule of thumb is to add 5-10% to your calculated volume.
Example: Adding 5% waste to 1.23 cubic yards: 1.23 cubic yards x 0.05 = 0.0615 cubic yards. Therefore, order 1.23 + 0.0615 = 1.2915 cubic yards. Round up to 1.3 cubic yards for your order.
In summary, you measure concrete needs by first calculating the cubic feet of the area you need to fill, then converting that figure to cubic yards, and finally adding a small percentage to account for waste.
