Plan The Pour Before You Order
Estimate the concrete required for slabs, patios, driveways, footings, piers, walls, columns and beams. Calculate cubic yards, cubic feet, approximate concrete bags and optional ready-mix material cost before you order.
Choose the project shape, enter dimensions and get concrete volume, bag quantity and optional cost instantly.
Estimate concrete for slabs, patios, driveways, garage floors, sidewalks, shed bases and other rectangular flatwork.
Finished slab length
Finished slab width
Use your supplier's local rate
Planning estimate only. Verify the finished dimensions, supplier ordering increments and final quantity before ordering.
Calculate concrete for cylindrical footings, Sonotubes, round piers, deck supports and similar concrete elements.
Foundation size depends on project loads, soil conditions, frost considerations and applicable design requirements.
Estimate concrete volume for foundation walls, basement walls, retaining-wall sections and other rectangular poured walls.
This calculator estimates material volume only. It does not determine structural wall thickness or reinforcement.
Estimate concrete for round columns, square columns and rectangular concrete beams.
Structural columns and beams should be sized according to an appropriate project design.
Estimate the volume normally used when discussing ready-mix concrete orders.
View the raw project volume before converting the result into cubic yards.
Estimate common 40 lb, 60 lb and 80 lb bag quantities.
Enter a local ready-mix rate to calculate a basic material estimate.
Concrete is a three-dimensional material, which means the quantity you need depends on volume rather than surface area alone. A patio can cover hundreds of square feet, but the final concrete quantity changes significantly depending on whether the slab is 3 inches, 4 inches, 5 inches or 6 inches thick.
Start by choosing the calculator that most closely matches the project shape. For a standard slab or driveway, use the Slab & Patio calculator. For cylindrical foundations, deck piers or Sonotube-style forms, use Footing & Pier. Poured vertical walls can be calculated using length, height and thickness, while columns and beams use their cross-sectional dimensions together with height or length.
Choose the calculator that matches the concrete shape.
Record finished concrete dimensions carefully.
Choose the amount of additional planning material.
View cubic feet, cubic yards and bags.
Confirm the final order with your concrete supplier.
The formula used by a concrete calculator depends on the shape of the concrete element. Rectangular slabs and walls use a simple length × width × depth calculation, while round piers and columns use the area of a circle.
Thickness is divided by 12 when it is entered in inches while length and width are in feet.
Convert the diameter to feet before calculating when the diameter is entered in inches.
Convert wall thickness from inches to feet before multiplication.
Beam width and depth entered in inches are converted to feet before volume is calculated.
One cubic yard contains 27 cubic feet because a yard is 3 feet long, 3 feet wide and 3 feet high. Therefore 3 × 3 × 3 = 27 cubic feet. The calculator calculates cubic feet first and then divides by 27 to display ready-mix volume in cubic yards.
Suppose you are building a rectangular patio that measures 20 feet long by 12 feet wide and the planned concrete thickness is 4 inches.
Four inches equals approximately 0.333 feet. The mathematical volume is therefore:
If you select a 10% planning allowance, the calculator multiplies the exact volume by 1.10. That produces an estimated ordering quantity of approximately 3.26 cubic yards.
This additional amount is intended to help account for normal construction variation such as minor differences in grade, form dimensions, uneven subgrade, small placement losses and concrete remaining in equipment.
The calculator changes the formula according to the shape of the concrete element.
Bagged concrete can be practical for small repairs, post bases, short walkways, small pads and projects where ready-mix delivery would be inconvenient or uneconomical.
The calculator estimates the number of bags using approximate yields for common 40 lb, 60 lb and 80 lb concrete products. Product yields vary between manufacturers, so use the number as a planning estimate and check the actual yield printed on the bag before purchase.
| Bag Size | Approx. Yield Used | Approx. Bags / yd³ | Common Application |
|---|---|---|---|
| 40 lb | 0.30 ft³ | About 90 | Small repairs and manageable batches |
| 60 lb | 0.45 ft³ | About 60 | Small pads, posts and DIY slabs |
| 80 lb | 0.60 ft³ | About 45 | Larger hand-mixed jobs |
Choosing between bagged concrete and ready-mix delivery is not simply a question of total volume. Labor, mixing equipment, access, placement speed and supplier requirements can all influence the best choice.
Bagged concrete offers flexibility because you can buy small quantities, store unopened bags temporarily and mix only what you need.
Ready-mix can be more efficient for larger continuous pours because the material arrives mixed and can be placed quickly.
Thickness has a direct relationship with concrete volume. If the surface area stays the same, increasing thickness increases the quantity of concrete required.
For example, a 6-inch slab uses 50% more concrete than a 4-inch slab with the same length and width.
The appropriate thickness, however, should not be selected simply by comparing concrete quantities. It depends on the project type, expected loading, subgrade, reinforcement strategy, climate and applicable requirements.
| Project | Common Planning Range | Typical Use | Key Considerations |
|---|---|---|---|
| Walkway | Approx. 3–4 in | Foot traffic | Base, drainage, soil and climate |
| Patio | Approx. 4 in | Furniture and people | Base preparation, slope and joints |
| Shed / Utility Pad | Approx. 4–6 in | Depends on structure | Equipment and structural loads |
| Driveway | Approx. 4–6+ in | Passenger vehicles | Vehicle loads, base and edge support |
| Garage Floor | Approx. 4–6+ in | Vehicles and storage | Loads, subgrade, reinforcement and joints |
| Heavy-Duty Slab | Project-specific | Heavy vehicles / equipment | Engineering may be required |
A concrete calculator can only be as accurate as the measurements entered. Before ordering concrete, take time to measure the actual finished concrete dimensions.
Do not automatically use the size of the excavation. Excavations may include extra space for forms, base material, drainage or working access. The calculator needs the dimensions of the concrete itself.
If forms and compacted base have already been installed, measuring at that stage can provide a more realistic estimate than measuring the site before preparation begins.
Uneven subgrade can create areas that are deeper than expected. Multiple depth checks can reveal whether the planned volume needs adjustment.
If one portion of a slab is 4 inches and another portion is 8 inches, calculate the two areas separately rather than using one average thickness.
Many patios, driveways and building slabs are not perfect rectangles. The easiest way to estimate an irregular layout is usually to divide the project into multiple simple shapes.
Imagine an L-shaped patio consisting of a main 20 × 10 ft rectangle plus an 8 × 6 ft extension. Calculate the two rectangles separately, then add the exact concrete volumes.
Circular and semicircular concrete areas require circle-based formulas. For complex landscaping or highly irregular layouts, divide the area into smaller measurable shapes and add the results together.
The exact volume calculated from project dimensions represents an ideal geometric shape. Real construction conditions are rarely perfectly uniform.
Reasons the final quantity may differ include:
The calculator therefore provides several ordering-allowance settings. A 10% option is useful for general planning comparisons, but it should not be treated as a mandatory percentage for every project.
Concrete prices differ significantly by location, supplier, order size, concrete specification, delivery distance and local market conditions.
Instead of forcing one fixed price, this page lets you enter your own ready-mix cost per cubic yard. The calculator then multiplies that price by the estimated ordering quantity.
The cost result represents a simple concrete-material estimate based only on the price per cubic yard you enter.
Calculating the correct concrete quantity is only one part of preparing a successful pour. The project should be ready before the concrete truck arrives or mixing begins.
The ground beneath the slab should be prepared according to the needs of the project. Soft or poorly prepared ground can contribute to movement, settlement and cracking.
Check length, width, elevation and alignment. Forms should be secure enough to resist the pressure of freshly placed concrete.
If the project uses rebar, mesh or other reinforcement, it should be positioned according to the project design before concrete placement.
Consider how concrete will move from the truck or mixer to the final placement location. Some projects may require wheelbarrows, chutes, powered equipment or pumping.
Concrete placement is time-sensitive. Screeds, floats, edgers, finishing tools and curing materials should be ready before the pour begins.
Once you know the estimated cubic yards, contact local ready-mix suppliers to discuss the actual order.
A supplier may ask about:
Tell the supplier if access is restricted or if the concrete must be pumped. These details can affect scheduling and total project cost.
Weather conditions can affect concrete placement, finishing and curing. Very hot, cold, windy or wet conditions can require additional planning.
High temperatures can increase the rate of moisture loss and shorten the time available for placing and finishing concrete.
Cold conditions can slow strength development and may require protection of freshly placed concrete.
Heavy rain during placement or finishing can create surface-quality problems. Check the weather forecast and discuss difficult conditions with experienced project professionals.
Concrete does not simply become fully ready as soon as the surface feels hard. Strength develops over time, and proper curing conditions help the concrete perform as intended.
Curing practices can vary according to project type, concrete mixture, weather and specification. Avoid treating a generic calculator as a curing schedule.
Where a project has structural, durability or safety requirements, follow the project documents, supplier guidance and applicable standards.
Square footage measures area, not concrete volume. Thickness must be included.
A 4-inch slab is not 4 feet thick. The calculator converts inch-based thickness automatically, but manual calculations must use consistent measurement units.
Excavation may include space that will be filled with base material or forms, not concrete.
Calculate different thickness zones separately to avoid over- or under-estimating the project.
This can count empty space. Divide irregular areas into smaller measurable shapes.
Manufacturer yields can differ. Verify the actual product information.
A mathematical order quantity does not necessarily match the supplier's minimum or ordering increment.
This calculator estimates concrete quantity only. It does not determine structural capacity, slab thickness, reinforcement, concrete strength or foundation sizing.
Material calculators are useful for estimating volume, but construction projects can involve requirements that go far beyond quantity.
For technical information, industry education and concrete-related standards, useful resources include the American Concrete Institute and the National Ready Mixed Concrete Association .
For structural or permit-related projects, follow approved plans, local requirements and qualified professional advice where appropriate.
You can return to the Concrete Calculator above at any time to compare different dimensions, thicknesses or ordering allowances.
Common questions about concrete volume, cubic yards, bag quantities, slabs, walls, footings and ordering.