Concrete Calculator
Please use this calculator to estimate the quantity of concrete required for your project.
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Please use this calculator to estimate the quantity of concrete required for your project.
When you’re estimating the cost of a decorative concrete slab, a useful figure to know is how much a yard of concrete will cover. Because ready-mix concrete is sold by volume measured in cubic yards, rather than square footage, the math can be a bit tricky. What’s more, when you pour concrete for a slab, it not only fills a square-foot area, it also fills it to a certain depth. The thicker the slab, the more concrete you’ll need to cover the same area.
To find the amount of concrete you need, use our concrete calculator or this simple volume formula: Length × Width × Thickness. Measure your project and multiply the dimensions to get cubic feet or meters. Divide by 27 to convert cubic feet to cubic yards. Using our concrete calculator ensures accuracy and saves time.
When ordering concrete from a ready mix supplier, one cubic yard is equal to 27 cubic feet. So, if your project measures 10 ft long, 10 ft wide, and 4 in thick, you'll need slightly more than 1 cubic yard of concrete to complete the job.
The amount of concrete you need for a 10x10 slab depends on how thick it will be. So, for a 4-inch slab you’ll need 1.24 cubic yards (56 80lb bags), but a 6-inch slab requires 1.85 yards (84 80lb bags). If your slab is a different size or thickness, use our calculator to determine the amount of concrete.
The number of 80 lb bags of concrete required for a slab depends on its size. Each 80-pound bag yields approximately 0.022 cubic yards of concrete. For a 4-inch thick, 100-square-foot slab, you'll need 56 bags. It's essential to calculate the volume based on your slab's dimensions.
Concrete is usually ordered in cubic yards, but if you're looking for concrete weight it varies depending on the type of mix being used. However, most ready mix suppliers estimate that a cubic yard of concrete weighs about 4,000 lbs. So if you need three yards, that would be around 12,000 lbs (3yds x 4,000lbs). Ask your supplier if you'd like to know the exact weight.
Never order the exact amount of needed concrete. Include a margin of safety.
A perfectly placed order of concrete will finish the job with a small amount left over. A 20 cubic yard order with 1 cubic yard left over is a good order. A 20 cubic yard order that comes up cubic yard short is not a good order.
Rule of thumb: add 1/4″ to the thickness of your slab for your slab concrete budget.
This assumes you have the job evenly graded to the right depth, and the grade is well compacted.
Odd shapes: Transform odd shapes into rectangles and they are suddenly easy to figure.
Figure driveway 14′ x 20′ and your estimate will be good. Here is why: The driveway is 16′ at the top and 12′ at the bottom. Through the center the width averages 14′.
Steps seem tricky to calculate but are not.
If there are three steps leading up to a porch. Use the slab calculator to figure the concrete needed for the porch surface. Use the footing calculator to calculate the sides of the porch and the steps.
