Plan The Load Before The Truck Arrives
Use this Ready Mix Concrete Calculator to estimate the cubic yards of concrete to order for slabs, driveways, patios, footings, walls and other pours. Add a practical ordering allowance, estimate full or partial truck loads and enter your local price per cubic yard for an instant material-cost estimate.
Choose a project, enter dimensions and estimate concrete to order, truck loads and optional ready-mix material cost.
Enter the finished length, width and slab thickness. Use quantity for repeated identical slabs.
Finished concrete length
Finished concrete width
Use actual planned thickness
Enter your local supplier quote
Confirm actual truck capacity
Estimate the concrete volume for cylindrical footings, piers and tube-form pours.
Calculate a rectangular wall or repeated wall sections using length, height and thickness.
Already know the project volume? Enter it in cubic yards, cubic feet or cubic meters and calculate the order quantity, truck loads and material cost.
A ready mix concrete calculator converts the finished dimensions of a pour into volume. Rectangular slabs and walls are calculated from length × width × thickness. Round piers use the cylinder formula. The exact volume is then converted to cubic yards because ready-mix concrete in the United States is commonly ordered by the cubic yard. An optional ordering allowance is added after the exact mathematical volume is found.
Measure the finished concrete dimensions, not the excavation size.
Choose slab, round footing, wall or known custom volume.
Choose a planning allowance for subgrade variation and placement loss.
Use the supplier's current price per cubic yard for a material estimate.
Enter truck capacity to estimate how many loads the order may require.
When thickness is measured in inches, divide inches by 12 before multiplying.
Suppose a driveway section measures 30 ft long × 12 ft wide × 5 in thick. First convert 5 inches to feet: 5 ÷ 12 = 0.4167 ft. The exact volume is approximately 30 × 12 × 0.4167 = 150 cubic feet. Divide by 27 to get about 5.56 cubic yards. With a 10% ordering allowance, the planning quantity becomes about 6.11 cubic yards.
From project measurements to the final delivery plan.
Ready mix concrete is concrete produced under controlled batching conditions and delivered to the jobsite in a mixer truck or other approved delivery system. For many slabs, foundations, driveways, commercial floors and larger residential pours, ready mix eliminates the need to hand-mix dozens or hundreds of bags on site.
The main estimating challenge is ordering enough material without paying for a large amount of unused concrete. That is why a ready mix concrete calculator separates the exact geometric volume from the planning order quantity. The exact number is useful for understanding the project. The adjusted number is more practical for discussing an order with a concrete supplier.
If your project is primarily a flat slab, our Concrete Slab Calculator provides a dedicated slab-focused estimate. If you need several project shapes or a bag comparison, use the broader Concrete Calculator.
The number of cubic yards depends on surface area and thickness. A small change in thickness can significantly change the order. For example, increasing a slab from 4 inches to 5 inches increases concrete volume by 25% when length and width stay the same. Increasing from 4 inches to 6 inches raises volume by 50%.
| Slab Size | Thickness | Exact Volume | With 10% Extra |
|---|---|---|---|
| 10 × 10 ft | 4 in | 1.23 yd³ | 1.36 yd³ |
| 20 × 20 ft | 4 in | 4.94 yd³ | 5.43 yd³ |
| 24 × 24 ft | 4 in | 7.11 yd³ | 7.82 yd³ |
| 20 × 20 ft | 6 in | 7.41 yd³ | 8.15 yd³ |
| 30 × 40 ft | 5 in | 18.52 yd³ | 20.37 yd³ |
These examples are mathematical planning values. The correct thickness is a design decision, not something the calculator chooses. Follow project plans, local requirements and qualified advice where appropriate.
Ordering exactly the mathematical volume can be risky because real forms, subgrade and excavations are rarely perfect. A planned allowance helps account for uneven base, form tolerances, small measurement errors, spillage and concrete left in the placement system. The appropriate allowance varies by project.
| Allowance | When It May Be Used | Planning Effect | Reminder |
|---|---|---|---|
| 0% | Pure mathematical comparison | No extra volume | Usually not a final order strategy |
| 5% | Simple, accurately formed pours | Small buffer | Still verify field conditions |
| 10% | Common planning scenario | Moderate buffer | Useful starting point, not a rule |
| 12–15% | Irregular or variable conditions | Larger buffer | Avoid using extra concrete as a substitute for measurement |
The calculator estimates the number of truck loads by dividing your planned order volume by the truck capacity you enter and rounding up to the next load. This is a scheduling estimate only. Mixer truck capacities, legal weight limits, batching practices and supplier policies can vary.
A project that needs 18 cubic yards with a 10 cubic-yard capacity would mathematically require two truck loads. A project needing 10.2 cubic yards would also require more than one 10-yard load, but that does not mean the second truck must arrive with 10 full yards. The supplier may schedule a smaller second load or apply a minimum/short-load charge.
The material-cost result multiplies the adjusted cubic-yard quantity by the price per cubic yard that you enter. It is intentionally user-driven because ready mix concrete prices are local and can change by region, mix design, quantity, season, delivery distance and supplier.
For this reason, treat the calculator's dollar result as a base material estimate. The supplier quote is the final source for actual delivered pricing.
Excavations can contain compacted base, drainage layers or working space that will not be filled with concrete. Measure the finished concrete dimensions inside the forms.
Subgrade that is low in one area can consume more concrete than expected. After base preparation, check depth at multiple points rather than relying on one measurement.
An L-shaped driveway can usually be divided into two rectangles. Calculate each rectangle and add the volumes. This avoids counting empty corners.
If a slab contains thickened edges, grade beams or equipment pads, calculate those zones separately. One average thickness can hide a meaningful quantity difference.
Forms can move and field conditions change. A final measurement before placing the order can prevent both shortages and unnecessary surplus.
Thickness has a direct linear relationship with volume. If the plan area stays the same, a slab that is 6 inches thick uses one and a half times as much concrete as a slab that is 4 inches thick. The calculator can show this immediately by changing only the thickness input.
| Project Type | Common Planning Range* | Volume Sensitivity | Design Note |
|---|---|---|---|
| Walkway / Patio | Often around 3–4 in | Every extra inch adds 25–33% vs thin slabs | Base, climate and loading matter |
| Residential Driveway | Often around 4–6+ in | 6 in uses 50% more than 4 in | Vehicle loads and edge support matter |
| Garage Floor | Often around 4–6+ in | Large floor areas amplify small thickness changes | Loads, reinforcement and joints matter |
| Structural / Heavy-Duty Slab | Project-specific | Can require substantial additional volume | Engineering may be required |
*Illustrative planning ranges only. The calculator is not a structural-design tool and does not select slab thickness.
Often practical for larger continuous pours where material must be placed quickly and consistently.
Useful for small jobs where only a modest volume is needed and truck delivery would be impractical.
There is no universal break-even volume because local material pricing, labor and delivery charges differ. Compare the supplier quote with the number of bags and mixing effort required for your project.
Correct volume is only part of a successful concrete pour. Before the truck arrives, confirm that the delivery route and placement method are realistic. Mixer trucks are heavy and need adequate clearance, turning space and ground support. Never assume the truck can drive onto a residential yard, prepared base or private driveway without supplier approval.
When direct truck access is impossible, a concrete pump can solve placement-distance or elevation problems, but pumping changes logistics and cost. Include that decision before ordering the ready mix.
Large pours require coordination between load volume, batching intervals and the placing/finishing crew. A simple truck-load count does not determine the correct delivery schedule. Concrete should arrive at a pace the crew can place, consolidate, screed and finish without creating avoidable delays or uncontrolled cold joints.
For a multi-load project, provide the supplier with the total cubic yards, desired first-truck time, approximate discharge rate, site conditions and any pumping arrangements. The supplier can help plan spacing between trucks based on plant distance and available fleet.
Confirm dimensions, elevations, slope and bracing before ordering.
Prepare and compact the subgrade/base as required for the project.
Install reinforcement, embeds and sleeves according to the project design.
Have enough people and tools to place and finish concrete promptly.
Do not use the arrival of the truck as the deadline for site preparation. Delays after batching can create quality and cost problems, especially if the truck is waiting while forms or reinforcement are still being adjusted.
A 4-inch slab is 0.333 ft thick, not 4 ft. The calculator handles this conversion for inch-based thickness fields.
If several identical pads or footings are being poured, include the quantity or calculate each group separately.
Thickened areas can add significant concrete. Estimate them as separate rectangular sections and add them to the slab volume.
Keep full precision during the geometric calculation. Apply practical ordering increments only after the exact total has been found.
Truck capacity varies. Enter the capacity provided by your supplier instead of relying on a generic value.
The calculator multiplies order volume by your price per cubic yard. It cannot know local delivery, pumping, standby or short-load charges unless you add them outside the calculator.
For broader concrete technical education and standards information, visit the American Concrete Institute (ACI). For ready-mixed concrete industry information, producer resources and education, visit the National Ready Mixed Concrete Association (NRMCA).
This calculator estimates material quantity only. It does not determine concrete strength, slump, air content, reinforcement, structural capacity, curing requirements or code compliance. Use project specifications and qualified professional guidance where required.
Answers to common questions about cubic yards, waste allowance, truck loads, pricing and ordering ready-mixed concrete.