Convert Project Dimensions Into Cubic Yards
Use this Concrete Yard Calculator to estimate how many cubic yards of concrete you need for slabs, patios, driveways, walls, footings, columns and piers. Enter the finished project dimensions, choose an optional extra allowance and get the exact volume plus an adjusted cubic-yard quantity for ready-mix planning.
Calculate cubic yards for rectangular, cylindrical and linear concrete pours, or convert a known volume directly into cubic yards.
Enter length, width and thickness to calculate the volume of one or more identical rectangular sections.
Finished concrete length
Finished concrete width
Concrete thickness, not excavation depth
Use diameter and height for round concrete elements such as piers, tube forms and cylindrical columns.
Calculate a long rectangular section using length, height/depth and thickness/width.
Already know the volume? Convert it between cubic feet, cubic yards and cubic meters, with an optional extra allowance.
A concrete yard calculator converts physical project dimensions into the amount of space that will be filled with concrete. The result is most often expressed in cubic feet, cubic yards or cubic meters. This is different from an area calculator: square feet describe surface area, while cubic units describe three-dimensional volume.
For a concrete slab, the three dimensions are length, width and thickness. For a wall, they are length, height and thickness. For a round pier, the calculation uses the circular cross-sectional area and the height or depth. Once the exact geometric volume is known, an optional planning allowance can be added to account for reasonable site variation and ordering needs.
The Concrete Yard Calculator above handles these conversions automatically and keeps cubic yards as the primary ordering unit. It is useful when planning patios, sidewalks, garage floors, driveways, foundations, footings, posts and many other common concrete projects.
The basic process is straightforward: measure the concrete itself, use the correct volume formula for the shape, convert thickness measurements into compatible units, then convert the final result into the ordering unit you need.
Measure the finished concrete length rather than the overall excavation.
Use the actual concrete width inside the forms.
Confirm slab thickness or wall thickness at multiple points where practical.
Apply the formula that matches the project geometry.
Choose a sensible extra allowance and confirm the final quantity with your supplier.
When all dimensions are in feet, the result is cubic feet. Divide cubic feet by 27 to convert to cubic yards.
Using the right formula matters because not every concrete project is a simple rectangle. The most common project shapes can be handled with a few standard geometric relationships.
Multiply the finished length by the finished width and by the concrete thickness. If thickness is measured in inches while length and width are in feet, divide the thickness by 12 first.
For a cylindrical pour, divide the diameter by two to find the radius. Convert the radius to feet, square it, multiply by π and then multiply by the height or depth.
A straight wall or continuous footing is also a rectangular prism. Multiply length by height or depth by thickness or width. For multiple identical sections, multiply the resulting volume by the number of sections.
A visual guide showing how a slab's three dimensions create volume and how that volume is converted for ready-mix planning.
Suppose you are planning a rectangular concrete slab that is 20 feet long, 12 feet wide and 4 inches thick. Convert 4 inches to feet: 4 ÷ 12 = 0.3333 feet. Multiply 20 × 12 × 0.3333 to get about 80 cubic feet.
To convert cubic feet to cubic yards, divide by 27. The exact volume is approximately 2.96 cubic yards. If a 10% planning allowance is selected, the adjusted quantity becomes about 3.26 cubic yards.
Concrete volume can be expressed in different units depending on your location, supplier and project. Understanding the relationship between these units helps prevent ordering errors.
Cubic feet are convenient when project dimensions are measured in feet. A slab calculation using feet for length, width and thickness produces a result directly in cubic feet.
Cubic yards are commonly used for ready-mix concrete quantities in the United States. Since one cubic yard equals 27 cubic feet, divide cubic feet by 27 to convert a project volume into cubic yards.
Cubic meters are the standard metric volume unit used in many countries. One cubic yard is approximately 0.7646 cubic meter, while one cubic meter is approximately 1.3079 cubic yards.
| Starting Volume | Cubic Feet | Cubic Yards | Cubic Meters |
|---|---|---|---|
| 1 ft³ | 1.000 | 0.0370 | 0.0283 |
| 1 yd³ | 27.000 | 1.000 | 0.7646 |
| 1 m³ | 35.315 | 1.3079 | 1.000 |
Thickness has a direct effect on concrete quantity. If the length and width stay the same, increasing thickness increases volume in the same proportion. A slab that changes from 4 inches to 6 inches thick uses 50% more concrete because 6 is 1.5 times 4.
This makes accurate thickness measurement especially important on larger slabs. A small difference in depth across hundreds of square feet can change the total cubic-yard requirement substantially.
| Slab Size | Thickness | Approx. Volume | Approx. Cubic Yards |
|---|---|---|---|
| 10 × 10 ft | 4 in | 33.33 ft³ | 1.23 yd³ |
| 10 × 10 ft | 5 in | 41.67 ft³ | 1.54 yd³ |
| 10 × 10 ft | 6 in | 50.00 ft³ | 1.85 yd³ |
| 20 × 20 ft | 4 in | 133.33 ft³ | 4.94 yd³ |
| 20 × 20 ft | 6 in | 200.00 ft³ | 7.41 yd³ |
These are volume examples, not structural thickness recommendations. Appropriate slab thickness depends on load, subgrade, reinforcement, local requirements and project design.
Do not automatically use the full excavation dimensions. Excavation space may include compacted stone, forms, drainage layers or working room that will not be filled with concrete.
Subgrade can be uneven. Measuring thickness or depth at several points can reveal low spots that would otherwise increase actual concrete consumption.
If part of a slab is 4 inches thick and another part is 8 inches thick, calculate the sections separately and add their volumes. Using one average thickness can hide important differences.
An L-shaped patio can usually be split into two rectangles. Curved layouts can often be approximated using rectangles, circles and partial circles. Add the resulting volumes together rather than treating empty space as concrete.
Real projects are often more complex than a single rectangle. The most reliable estimating approach is to divide the pour into simple shapes that can be measured independently.
Split an L-shaped area into two rectangles, calculate each rectangle using the slab calculator and add the exact volumes before applying an allowance.
For a circular section, use the cylinder formula with the patio thickness as the cylinder height. For a semicircle, calculate the full circle-based volume and divide by two.
Calculate each step, landing or level separately if dimensions differ. This keeps the estimate traceable and makes it easier to check measurements before ordering.
The exact geometric volume is the amount of space described by the measurements. The amount ordered can be slightly higher if you choose an allowance for field conditions, minor subgrade variation or practical placement needs.
There is no universal percentage that is correct for every project. A carefully formed, uniform slab may require less contingency than a rough excavation with variable depth. The calculator lets you compare 0%, 5%, 10%, 12% and 15% so you can see how the selected allowance changes the result.
For delivered concrete, use the Ready Mix Concrete Calculator to add truck-load and cost planning. Always confirm final ordering increments, minimums and delivery policies directly with the supplier.
Volume is the starting point whether you plan to order ready-mix or use bagged concrete. Bagged products are sold by weight, but each product also has a stated yield describing how much mixed concrete it produces.
For a small project, convert the required volume into cubic feet and divide by the actual yield printed on the bag. Product yields vary, so the manufacturer label should be the final reference rather than a generic assumption.
Often practical for small repairs, post holes and small pads where mixing manageable batches is convenient.
Often more practical for larger or continuous pours where consistent delivery and placement speed are important.
Measure each rectangular or curved section and keep thickness consistent with the project design.
Separate widened aprons, thickened edges or different-depth sections before adding totals.
Use wall/footing mode for strips and cylinder mode for round piers or tube forms.
Multiply wall length by height by thickness and subtract major openings only when appropriate.
The answer depends on three things: the footprint of the project, the concrete thickness or depth, and any extra allowance you choose for real-world conditions. A cubic yard is a volume measuring 3 feet × 3 feet × 3 feet, or 27 cubic feet. Because ready-mix concrete in the United States is commonly discussed and sold by the cubic yard, converting the finished project dimensions into yards is one of the most useful planning steps before requesting a supplier quote.
For a rectangular slab, multiply length in feet by width in feet by thickness in feet, then divide the result by 27. If thickness is entered in inches, divide it by 12 first. The calculator above performs those conversions automatically and can also apply an optional percentage allowance after the exact geometric volume is known.
For inch-based thickness: convert inches to feet by dividing by 12 before calculating volume.
Supplier order increments, minimum-load policies, delivery fees and truck capacity can affect the final quantity you actually purchase. The mathematical result from a Concrete Yard Calculator is therefore the starting point, not a substitute for confirming the order with the ready-mix producer. Measure carefully, separate areas with different depths, and discuss the final rounded quantity with the supplier before scheduling the pour.
| Volume | Cubic Feet | Cubic Yards | Approx. Cubic Meters |
|---|---|---|---|
| Small quantity | 13.5 ft³ | 0.50 yd³ | 0.382 m³ |
| One cubic yard | 27 ft³ | 1.00 yd³ | 0.765 m³ |
| Three cubic yards | 81 ft³ | 3.00 yd³ | 2.294 m³ |
| Five cubic yards | 135 ft³ | 5.00 yd³ | 3.823 m³ |
| Ten cubic yards | 270 ft³ | 10.00 yd³ | 7.646 m³ |
These conversions are useful when drawings, supplier documents or project notes use different volume units. For cost planning after calculating yards, continue to the Concrete Cost Calculator.
A volume calculator estimates material quantity only. It does not determine structural capacity, concrete strength, reinforcement, joint spacing, curing requirements or compliance with local rules.
For technical concrete information and industry education, useful authoritative resources include the American Concrete Institute and the National Ready Mixed Concrete Association.
For structural or permit-related work, follow approved plans, project specifications, local requirements and qualified professional guidance where needed.
Use the calculator that matches the next decision in your project.
Common questions about cubic yards, slab yardage, ready-mix quantities, cubic-foot conversion, round piers and ordering allowances.