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Slab Dimensions
Standard concrete thickness is 4 inches. Increase this to six inches to better handle heavy loads.
feet feet


How many pre-mix bags:
40# Bags:
60# Bags:
80# Bags:


Footing Dimensions
inches inches feet


How many pre-mix bags:
40# Bags:
60# Bags:
80# Bags:

Enter the diameter and height of your concrete column to calculate the number of cubic yards and concrete bags needed to complete your project.

Column Dimensions
inches inches


How many pre-mix concrete bags:
40# Bags:
60# Bags:
80# Bags:



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Concrete, Pouring and Pricing:

Use this free concrete calculator to determine how much concrete you need. Knowing how much concrete is needed for a job is incredibly important. Learn how to correctly calculate how much concrete mix you will need for your job.


What equation should I use to find out how much concrete I need?

How to calculate concrete:

  1. Determine how thick you want the concrete
  2. Measure the length and width that you’d like to cover
  3. Multiply the length by the width to determine square footage
  4. Convert the thickness from inches to feet
  6. Convert cubic feet to cubic yards by multiplying by .037

Here’s what the math looks like for a 10’ by 10’ concrete patio:

  1. 10 x 10 = 100 square feet
  2. 4 ÷ 12 = .33
  3. 100 x .33 = 33 cubic feet
  4. 33 x .037 = 1.22 cubic yards

Essentially you are solving for volume and then converting to cubic yards. For concrete, the formula for volume is as follows: length x width x thickness.


Use the following yields per each bag size:

  • 40 pound bag yields .011 cubic yards
  • 60 pound bag yields .017 cubic yards
  • 80 pound bag yields .022 cubic yards


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

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

Bagged concrete is ideal for:

  • Pouring small slabs for sidewalks or patios
  • Setting posts for fences or mailboxes
  • Making repairs to foundation walls, walkways or steps
  • Pouring small curbs, steps, or ramps
  • Footings for decks, pergolas, walls and more

If you’re purchasing bagged concrete you may be able to have it delivered, but if it is only a few bags you’ll be responsible for transporting it yourself. You’ll also need additional equipment for mixing the concrete. A rented mixer can be very helpful, but a wheelbarrow works for just a few bags.

Ready mixed concrete by the yard is good for:

  • Large patios, driveways, pool decks and more
  • Foundation slabs for a house
  • Parking lots or commercial sidewalks

If you’re planning to order concrete from a ready mix supplier, they’ll need to know how many yards of concrete to deliver. Many ready mix companies will have a minimum order of 1 yard, and will charge shortage fees when ordering partial batches. The average truck holds between 9 and 11 yards total. If your project requires more concrete, multiple trucks will be necessary.


Atlanta Brick & Concrete in Atlanta, GA

Calculating the amount of concrete needed for slabs (including odd shapes)





Calculating the amount of concrete needed for footings






Estimating concrete steps



Here is an example:




Repeat this for added layers of steps.

3' x 3' Porch

Calculating the amount of base fill





Extra costs of coming up short of concrete

  • Overtime for the crew
  • A short load charge from the ready mix supplier

Three steps to ordering enough concrete:

  • Use the concrete calculator
  • Add a margin of safety

Rule of thumb for margin of safety:

If your order is Order this much extra
1-5 cubic yards .5-1 c.y. extra
6-10 c.y. 1 c.y. extra
11-20 c.y. 1-1.5 c.y. extra


Requesting your ready mix supplier to visit your site



Last updated: April 23, 2018

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