Concrete Calculator - Quickly Estimate How Much You Need

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.

What the Pros Say: Use the Magic Number

If you're pouring a 4-inch slab and want a quick estimate, there's an easy way:
"The magic number is 81. Take the total square footage of the job and divide it by 81 to get the number of cubic yards you need."
(Example: 200 sq ft ÷ 81 = 2.46 yards for a 4-inch slab)

— Tim Seay, Decorative Concrete of Virginia
How to Measure Concrete the Easy Way

What is the standard thickness of concrete?

The standard thickness of concrete varies depending on its use. For residential slabs, 4 inches is typical for patios, walkways, and driveways. Garage floors and heavy-duty driveways often use 5-6 inches. Commercial applications may require 6-8 inches or more.

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.

What the Pros Say: Let the Ready-Mix Plant Do the Math

"You can just call your local Ready-Mix plant, give them your square footage and thickness, and they’ll figure it up for you."

— Jeff Hershberger, Deco-Crete Supply
The Easiest Way to Calculate Concrete Yardage!

This is a great option for larger projects like driveways or patios, especially if you're not confident doing the math yourself.

Adding color to your concrete?

If you’re using integral color, you’ll need to calculate pigment based on the number of cubic yards you’re pouring. Use the Solomon Colors Pigment Calculator to get an accurate dose based on your mix design, color choice, and total yardage. Using the right amount of pigment is key to achieving consistent, even color.

How much does concrete cost per square foot?

Expect to pay between $5.50 and $9.00 per square foot to have a plain concrete slab poured. To get an even better idea of how much your project will cost, get quotes from local contractors that can come see the site.

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.

More Resources:

21 Questions About Concrete
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