Concrete Calculator – How Much Concrete Do You Need?

Calculate the concrete material needed to pour a slab, patio, footing, column, or post-fill-project in cubic yards or pre-mix bags, and estimate the cost of materials.

How to Calculate Concrete

Steps to Calculate Cubic Yards of Concrete

• Measure the length, width, and height of the slab, footing, or column.

  If the area is complex or multiple pours are needed, break the project into smaller pieces and calculate the concrete needed for each individually.

  For instance, when measuring a slab that is not a simple rectangle, try breaking it into different sections and measure the yards needed for each section separately.

  
• Convert dimensions to feet if they aren’t already. Conversion calculators make it easy to convert inches, yards, or meters to feet.
• Multiply the width times the length times the height (W × L × H), or use our volume calculator to find the cubic feet.
• Convert the volume to cubic yards from cubic feet. To do so, divide the cubic footage by 27 to get the yards of concrete needed.^[1]
• Round up to the nearest yard as most suppliers will likely not sell fractions of a yard. It is worth asking your supplier if they will sell a partial yard of material, but most do not.

• Estimate how many pre-mixed bags are needed for smaller projects when it isn’t practical to order a truckload of concrete.

  The table below shows the coverage of different sizes of pre-mix bags. On average, it will take 90 40lb bags, 60 60lb bags, or 45 80lb bags to fill one cubic yard of concrete.

• Add 5%-10% additional material to account for settling, spillage, and waste.^[2] This will ensure you can complete your project in a single pour without needing to get more concrete to complete the project if you’re short.

How Much is a Yard of Concrete?

One cubic yard is equal to the volume of a cube with edges that are one yard (three feet) in length.

You might be wondering just how much concrete is in a cubic yard? A cubic yard is equal to 27 cubic feet or 46,656 cubic inches, or 45 80lb bags.

Concrete Cubic Yards Formulas

Use the following formulas to calculate the concrete needed for various types of pours.

How Many Bags of Concrete do you Need?

So, how many bags of concrete do you need?

Calculating bags is a little less straightforward since each bag size will fill different volumes. Use the calculator above to estimate how many bags you’ll need.

The table below shows the average fill in yards for various pre-mix bag sizes. Check the bag you’re using to find the exact fill-rate for the product.

Table showing the number of pre-bags of concrete needed to fill a volume measured in cubic yards.

Bag Size	Pre-mix Bags Needed to Fill
	1/4 cu yd	1/2 cu yd	3/4 cu yd	1 cu yd
40 lb bags	23	45	68	90
60 lb bags	15	30	45	60
80 lb bags	12	23	34	45

How to Calculate Concrete Costs

The cost of a concrete project varies depending on the project’s size and scope, your geographic location, and the type of material used.

Concrete Cost per Yard

Ready-mix concrete typically starts around $115 per yard but could cost upwards of $150 or more, depending on the mix and your location. Consider that there will likely be additional fees for ready-mix for smaller projects, such as delivery or short-load fees.^[3]

Cost per Bag

Pre-mix bags usually range from $2.50 to $7, making them a cost-effective choice for small projects.

Average price of concrete.

ready-mix:	$115 – $150 per cu yd
pre-mix 40 lb bags:	$2.50 – $5 per bag
pre-mix 60 lb bags:	$3 – $6 per bag
pre-mix 80 lb bags:	$4.50 – $7 per bag

The average cost to install a concrete slab is $6 – $20 per square foot. Besides the cost of concrete and materials, there are also labor costs for preparing the area, the pour, and finishing.

A standard brush finish will likely be on the low end of the price range, while a decorative finish with coloring will be on the high end of the range. Consider getting a professional concrete installation estimate from contractors in your area for a more accurate cost estimate.

Tips for Preparing for a Ready-Mix Concrete Pour

Much of the work to pour concrete is done before the truck even arrives at the project. You’ll need to measure and lay out the site and install forms to create the edges of a slab or contain a footing.

Use rebar or fiber/steel mesh to reinforce the concrete and to prevent cracking in the future. Use our rebar material and reinforcing mesh calculators to estimate the amount of reinforcement needed for your project.

Ensure the installation team is ready for the installation and able to begin as soon as the truck arrives to avoid having it set up before the project can be completed and minimize idle time.

If you’re curious how much it weighs, try our concrete weight calculator.