Concrete Calculator - Quickly Estimate How Much You Need

Use these free concrete calculators to quickly estimate how much concrete you need for slabs, footings or columns. It is a good idea to overestimate the amount of concrete needed so you won't come up short on the jobsite.

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CONCRETE CALCULATOR FAQs

How do I calculate how much concrete I need?

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.

How much is 1 yard of concrete?

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.

Related: How Many Square Feet in a Yard of Concrete?

How much concrete do I need for a 10x10 slab?

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.

How many 80 lb bags of concrete for a slab?

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.

How many cubic feet is a 50-pound bag of concrete?

A 50-pound bag of concrete yields approximately 0.375 cubic feet. This estimation is useful when calculating the amount of concrete needed for a project, but consider the specific dimensions of your slab to ensure you have the right quantity.

Should I order concrete by the yard from a ready mix company or just use bags?

Larger jobs such as concrete driveways are easier to complete when ordering by the yard, rather than trying to mix bag after bag by hand. For smaller jobs, like a concrete walkway, small patio or footings, you should calculate the number of concrete bags instead.

How much does concrete weigh?

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.

CONCRETE ESTIMATING TIPS

• 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.

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