Concrete Calculator

By HomeAdvisor

Updated January 7, 2021



Dimensions (in ft.)

This concrete estimator will help you find out how much concrete you need by cubic yard. Plus, find how much 80lb and 60lb bags cover, estimate the slab area for triangular or octagonal shapes and more.

On This Page:

  1. Tips on Measuring for Concrete
  2. Different Kinds of Concrete
  3. How to Buy Concrete
  4. Cost Factors
  5. FAQ
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Tips on Measuring for Concrete

Your measurement methods will shift depending on the shape of your future concrete slab. For example, you’ll measure a rectangular shape using length and width. A circular shape requires that you find the diameter.

Once you find the dimensions of your slab, input them into the calculator along with the thickness. Enter your project area measurements rounded to the nearest foot. If you’d rather do the math yourself, simply measure length, width and height in feet. Then multiply these dimensions together. Divide the resulting number by 27 to find the cubic yardage.

Once you have your measurement in cubic yards, consult our True Cost Guide for concrete prices.

Different Kinds of Concrete

There are several kinds of concrete available for different home projects. If you’re not sure which type to get, don’t hesitate to talk to a concrete pro near you. Here are a few common varieties of concrete:

  • Quick-set: Hardens in 20 to 40 minutes. Best for small projects.
  • Regular-set: 24 to 48 hour set time. Used more for large projects.
  • High-strength: Usually sets in 10 to 12 hours. Works well for foundation.
  • Crack-resistant: This is a durable option that works well for walkways.
  • Polymer: Uses epoxy binder to harden. Benefits depend on the type of resin used, but can include heat and weather resistance.

How to Buy Concrete

If you have a larger job, like a building a driveway or pool deck, it’s probably best to order concrete by the cubic yard or hire a concrete delivery service. For smaller jobs, like setting posts for fences or small curbs, mixing bags of concrete should be sufficient.

Always make sure to order a little extra concrete in case of mistakes or uneven ground.

Cost Factors

There are several things that can affect the cost of your concrete project, including:

  • How complicated the project is: stairs will likely cost more than a slab, for example.
  • Materials: polymer concrete is often more expensive.
  • Labor prices: jobs that take longer and need more workers will have a higher price.
  • Extra strength: adding rebar or mesh to the concrete will up the cost.
  • Additional tasks: if pros need to remove debris, get rid of your existing patio or dig before starting, it will be more expensive.


How much concrete do I need? How many bags do I need?

The amount of concrete you need varies by project. One 80lb-bag covers an area of about 2 square feet, for a slab 4 inches thick. Two 60lb-bags of concrete cover an area of about 2 square feet for a slab that is 6 inches thick.

How much is a truckload of concrete?

A truckload of concrete can usually hold a maximum of 10 cubic yards.

How much is concrete a yard?

The cost of concrete per cubic yard depends on which brand you purchase, but usually costs about $110 for bags.

How many 80lb bags of concrete make a yard?

It takes about 41 bags of concrete to fill a cubic yard. Always plan to buy a few bags more than the exact required amount in case of mistakes.

How do I calculate how much concrete I need for a slab?

To calculate the amount of concrete you need for a slab, you should find the cubic yardage of the area you will be filling. Just follow these steps:

  1. Measure the area in feet.
  2. Multiply length by width, and then by thickness.
  3. Divide the resulting number by 27 to find cubic yards.
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  1. lee padgett, November 9:

    want to know how much to order concrete

  2. Mickey, January 22:

    Cost to install a concrete stairwell down on the outside of a basement concrete wall break through to make a door way

  3. Concrete Logan, October 3:

    Its always a good idea to double check yourself when ordering concrete. Too much concrete and you overpay not enough and you are waiting for more or cant get it. Most ready-mix companies will calculate it for you if you call in with measurements.

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