Concrete Cubic Yard Calculator
Knowing how many cubic yards of concrete you need is essential when planning a slab, driveway, patio, column, footing, or other concrete project. Our Concrete Cubic Yard Calculator helps you quickly estimate concrete volume using your project's dimensions while also accounting for a waste factor and concrete price.
The calculator supports three common concrete shapes: rectangular slabs, cylindrical columns, and circular slabs. Depending on the selected shape, simply enter the required dimensions. The calculator provides the volume in cubic feet, converts it to cubic yards, adds your selected waste percentage, and estimates the concrete material cost.
This concrete yard calculator is useful for homeowners, DIYers, builders, landscapers, and contractors who want a convenient preliminary estimate before purchasing concrete. It can also help you compare different project dimensions, waste allowances, and concrete prices before requesting a supplier quote.
How to Use the Concrete Cubic Yard Calculator
Using the calculator takes only a few steps. First, choose the appropriate project shape from the Shape Type menu. Select Slab/Rectangle for rectangular concrete areas, Cylinder/Column for cylindrical structures, or Circular Slab for round concrete surfaces.
For a rectangular slab, enter the length and width in feet and the depth in inches. For a cylinder or column, enter the diameter and height in feet. For a circular slab, enter the radius in feet and thickness in inches.
Next, enter your waste factor. The calculator provides a default value of 10%, but you can change it based on your project requirements. Finally, enter the concrete price per cubic yard. The default value is $150 per cubic yard and can be replaced with the current price from your local concrete supplier.
Select Calculate to see the estimated volume and cost. Your results include the original volume in cubic feet, original volume in cubic yards, cubic yards after the waste factor is added, and estimated concrete cost.
How to Calculate Cubic Yards of Concrete
Concrete quantity is calculated as volume rather than just surface area. A project's length and width tell you its area, but depth or thickness is also required to determine how much concrete will fill that area.
For a rectangular slab, the basic formula is:
Cubic Feet = Length × Width × Depth in Feet
Since this calculator asks for slab depth in inches, the depth is converted to feet first:
Depth in Feet = Depth in Inches ÷ 12
After finding the cubic-foot volume, the calculator converts the result to cubic yards. One cubic yard contains 27 cubic feet.
Cubic Yards = Cubic Feet ÷ 27
This conversion is important because ready-mix concrete is commonly ordered and priced by the cubic yard.
Concrete Slab Calculation Example
Suppose you are planning a concrete slab measuring 20 feet long and 12 feet wide with a depth of 4 inches.
First, convert 4 inches to feet:
4 ÷ 12 = 0.3333 feet
Next, calculate the volume:
20 × 12 × 0.3333 ≈ 80 cubic feet
Now convert cubic feet to cubic yards:
80 ÷ 27 ≈ 2.96 cubic yards
If you enter a 10% waste factor:
2.96 × 1.10 ≈ 3.26 cubic yards
At $150 per cubic yard, the estimated concrete material cost is approximately:
3.26 × $150 ≈ $488.89
The calculator performs all of these steps automatically based on the measurements, waste factor, and concrete price you provide.
How to Calculate Concrete for a Cylinder or Column
Concrete columns, cylindrical footings, and similar round structures require a different volume formula. The calculator uses the diameter to determine the radius and then calculates the volume of a cylinder.
The formula is:
Volume = π × Radius² × Height
Radius equals half of the diameter.
For example, consider a cylindrical concrete column measuring 2 feet in diameter and 6 feet high. Its radius is 1 foot.
The volume is approximately:
3.1416 × 1² × 6 = 18.85 cubic feet
Converted to cubic yards:
18.85 ÷ 27 ≈ 0.70 cubic yards
The selected waste percentage is then added before the estimated concrete cost is calculated.
How to Calculate Concrete for a Circular Slab
The calculator can also estimate concrete for round slabs. This can be useful for circular patios, equipment bases, landscaping features, and other round concrete areas.
For a circular slab, enter the radius in feet and thickness in inches. Remember that radius is the distance from the center of a circle to its outside edge. It is half the diameter.
The calculation uses:
Volume = π × Radius² × Thickness
The thickness is converted from inches to feet before calculating cubic feet.
For example, a circular slab with a 5-foot radius and 6-inch thickness has a thickness of 0.5 feet.
Its volume is approximately:
3.1416 × 5² × 0.5 = 39.27 cubic feet
That equals approximately:
39.27 ÷ 27 = 1.45 cubic yards
A waste factor can then be applied to estimate the total quantity needed.
What Is a Concrete Waste Factor?
A concrete waste factor is an additional percentage added to the theoretical volume of a project. Actual site conditions do not always match ideal measurements. Uneven excavation, variations in forms, subgrade differences, spillage, and changes in concrete thickness can increase the amount needed.
For example, if a calculation produces exactly 5 cubic yards and you apply a 10% waste factor:
5 × 1.10 = 5.5 cubic yards
The calculator allows you to adjust the waste percentage instead of automatically assuming the same allowance for every project.
A 10% default can be useful for preliminary estimates, but the appropriate allowance depends on the job. For important pours, confirm the final order quantity with your contractor or ready-mix supplier.
How Much Is a Cubic Yard of Concrete?
A cubic yard is a three-dimensional unit of volume measuring 3 feet long by 3 feet wide by 3 feet high.
That means:
1 cubic yard = 27 cubic feet
Concrete prices vary considerably by location, supplier, concrete mix, order size, delivery distance, and other factors. This calculator lets you enter a price per cubic yard rather than relying on a fixed national price.
For the most useful estimate, contact a local concrete supplier for the current per-yard price and enter that amount into the calculator.
How the Concrete Cost Estimate Works
The calculator bases its estimated cost on the volume after the waste factor has been included.
The basic calculation is:
Estimated Cost = Cubic Yards Including Waste × Price Per Cubic Yard
For example, if your total requirement including waste is 4.5 cubic yards and the concrete price is $175 per cubic yard:
4.5 × $175 = $787.50
Keep in mind that this is a concrete material estimate. It does not automatically account for all costs associated with installing concrete.
A supplier may charge for delivery, small orders, fuel, special mixes, waiting time, pumping, or other services. A complete project budget may also need to include forms, reinforcement, base material, excavation, labor, finishing, equipment, permits, taxes, and removal of existing materials.
Tips for Measuring a Concrete Project
Accurate measurements are one of the most important parts of estimating concrete. Measure the actual area that will receive concrete whenever possible instead of relying exclusively on approximate dimensions.
For slabs, take measurements at multiple locations when an area is irregular. If the project consists of several rectangular sections, calculate each section separately and add their volumes together.
Pay close attention to measurement units. This calculator expects slab length and width in feet but depth in inches. Cylinder diameter and height are entered in feet. Circular slab radius is entered in feet and thickness in inches.
Also verify whether you have measured a circle's radius or diameter. Accidentally entering the diameter as the radius can significantly overestimate the required concrete.
Why Concrete Depth Matters
Even a relatively small change in slab thickness can make a major difference in total concrete volume, particularly across a large surface.
For example, a 4-inch slab and a 6-inch slab with identical length and width do not require the same amount of concrete. A 6-inch thickness is 50% greater than a 4-inch thickness, so the theoretical concrete volume is also 50% greater.
Always use the appropriate slab thickness for the intended application and follow applicable plans, engineering specifications, and building requirements.
Cubic Yards vs. Square Feet
Square feet and cubic yards measure different things. Square feet measure two-dimensional surface area, while cubic yards measure three-dimensional volume.
For example, knowing that a driveway covers 500 square feet is not sufficient to determine its concrete volume. You must also know the intended depth.
This is why a cubic yard calculator needs length, width, and depth—or equivalent dimensions—to produce an accurate volume estimate.
Using the Estimate When Ordering Ready-Mix Concrete
The calculator is particularly helpful for preparing a preliminary ready-mix concrete estimate. Once you know the cubic-yard requirement including your chosen waste factor, contact a supplier to confirm pricing, minimum order quantities, delivery availability, and ordering practices.
Suppliers may sell concrete in specific increments and can have different policies for small loads. Your theoretical calculator result therefore does not necessarily equal the exact quantity that a supplier will recommend or invoice.
For structural or high-value construction, verify the measurements and required concrete quantity with the appropriate construction professional before placing an order.
Frequently Asked Questions
- What does the Concrete Cubic Yard Calculator calculate?
It calculates concrete volume in cubic feet and cubic yards. It also adds a selected waste percentage and estimates concrete material cost using the price per cubic yard. - How many cubic feet are in a cubic yard of concrete?
There are 27 cubic feet in one cubic yard. - How do I calculate cubic yards for a concrete slab?
Multiply length by width by depth after converting all dimensions to feet. Divide the resulting cubic feet by 27 to get cubic yards. - Can I calculate concrete for a circular slab?
Yes. Select Circular Slab, then enter the radius in feet and thickness in inches. - Can the calculator estimate concrete for columns?
Yes. Choose Cylinder/Column and enter the column's diameter and height in feet. - What is the difference between radius and diameter?
The diameter runs across the entire circle through its center, while the radius measures from the center to the edge. Radius is half the diameter. - Does this concrete calculator include a waste factor?
Yes. You can enter a waste percentage, and the calculator adds it to the calculated cubic-yard volume. - Is a 10% concrete waste factor always necessary?
No. The calculator uses 10% as a default, but the appropriate allowance depends on measurements, site conditions, project design, and supplier practices. - How is the estimated concrete cost calculated?
The total cubic yards after adding your waste factor are multiplied by your entered concrete price per cubic yard. - Does the estimated cost include concrete delivery?
No. Delivery charges and other supplier fees are not calculated separately unless they are already incorporated into the per-yard price you enter. - Why is slab depth entered in inches?
Slabs are commonly described using thicknesses such as 4 or 6 inches. The calculator automatically converts the entered depth from inches to feet for the volume calculation. - How much concrete do I need for a 20 × 20 slab?
The answer depends on slab depth. A 20-by-20-foot area alone provides square footage, not volume. Enter the length, width, and planned depth into the calculator for a cubic-yard estimate. - Can I use the calculator for a concrete driveway or patio?
Yes. Rectangular driveways, patios, sidewalks, pads, and similar areas can be estimated using the Slab/Rectangle option. Complex areas may need to be divided into separate sections. - Why might the delivered concrete quantity differ from my calculated amount?
Site conditions, excavation variations, actual slab thickness, waste, supplier order increments, and measurement differences can affect the final quantity. - Is the Concrete Cubic Yard Calculator accurate enough for ordering concrete?
It provides a mathematical estimate based on the measurements you enter. For major, structural, or expensive pours, confirm project dimensions, waste allowance, specifications, and final order quantity with your contractor, engineer, or concrete supplier.