Concrete Calculator
Estimate concrete quantity, volume, bags, and ready-mix cost for slabs, round footings, tubes, curb-and-gutter sections, and stairs. Plan rectangular-driveway materials and entered local material costs below.
Concrete Calculator
Concrete calculator results
Enter concrete dimensions to estimate volume, bags, and ready-mix cost.
Concrete quantity formula
Area = Length × Width
Cubic yards = Area (sq ft) × Slab thickness (in) ÷ 12 ÷ 27 × (1 + Waste factor%)
Bags = Ceil(Volume ÷ yield)
Ready-mix cost = Cubic yards × Optional ready-mix price
Concrete driveway planner
Driveway planner uses the concrete page's selected unit system.
Estimate concrete, rebar, stone, forms, stakes, and entered material costs for a rectangular driveway.
Driveway material plan results
Enter driveway dimensions to estimate materials and entered costs.
- Perimeter
- -- linear ft
- Rebar
- -- sticks
- Linear rebar
- -- linear ft
- Forms
- -- linear ft
- Stakes
- -- each
Material cost
- Concrete Material cost
- --
- Stone Material cost
- --
- Rebar Material cost
- --
- Forms Material cost
- --
- Stakes Material cost
- --
- Total entered costs
- --
Complete material total requires all five prices.
Driveway material formula
Area = Driveway length × Driveway width
Concrete = Area × Concrete depth × (1 + Waste factor ÷ 100)
Stone = Area × Compacted base depth × (1 + Base ordering allowance ÷ 100)
Rebar grid uses #4 bars, your spacing, and your edge inset.
Forms follow the driveway perimeter; stakes are estimated at 8 ft spacing.
Bags vs ready-mix concrete
Bagged concrete is handy when the pour is small enough to mix at a steady pace. It works well for small pads, repairs, setting posts, and projects where a truck cannot reach the site.
Ready-mix is usually the cleaner choice once the bag count gets high. A single cubic yard is roughly 45 eighty-pound bags, so even a modest slab can turn into a lot of lifting and mixing.
The calculator shows both views because homeowners often need the same quantity in two buying languages: bags at the store, cubic yards when calling a ready-mix supplier.
Concrete quantity examples
These are planning examples only. Use your actual dimensions, project shape, waste allowance, and supplier pricing in the calculator. The shape selector also covers round footings, hollow tubes, curb-and-gutter sections, and solid filled-step estimates.
Swipe or scroll horizontally to see more columns.
| Project | Area | Thickness | Concrete estimate |
|---|---|---|---|
| 10 x 10 ft patio | 100 sq ft | 4 in | About 1.36 cu yd with 10% waste |
| 12 x 20 ft slab | 240 sq ft | 4 in | About 3.26 cu yd with 10% waste |
| 20 x 30 ft driveway slab | 600 sq ft | 5 in | About 10.19 cu yd with 10% waste |
Concrete for driveways and pavement work
The driveway planner above estimates rectangular-driveway quantities for concrete, compacted base stone, #4 rebar, perimeter forms, stakes, and any local material prices you enter. It is a planning estimate, not an installed quote: excavation, finishing, curing, demolition, delivery, and contractor labor remain outside the result.
If you are still choosing between materials, read the asphalt vs concrete driveway guide. If you already chose asphalt, use the asphalt driveway cost calculator for installed driveway ranges.
A slab also needs a stable base. For aggregate under concrete, pavers, or asphalt, the road base calculator can estimate tons and cubic yards from depth and density.
Estimating a long curb or curb-and-gutter section instead of a slab? Use the concrete curb calculator for rectangular or trapezoidal cross-sections.
Protecting an existing slab instead of pouring one? Use the concrete sealer calculator for gallons and whole containers based on the product label.
Sources and assumptions
- QUIKRETE Concrete Mix data sheet — 40/60/80 lb bag yield references, checked July 6, 2026.
- CEMEX ready-mix concrete calculator — Cubic-yard ordering and ready-mix planning notes, checked July 6, 2026.
FAQ
How do I calculate concrete for a slab?
Multiply length by width to get area. Convert thickness from inches to feet, multiply by the area to get cubic feet, then divide by 27 to get cubic yards. Add a waste allowance before ordering.
How many 80 lb bags are in a cubic yard of concrete?
An 80 lb bag that yields about 0.60 cubic feet works out to about 45 bags per cubic yard. Always check the yield printed on the exact product you plan to buy.
Should I use bags or ready-mix concrete?
Bags are practical for small repairs, post holes, and very small slabs. Larger slabs usually make more sense as ready-mix because mixing dozens of bags by hand is slow and hard to keep consistent.
Does the calculator choose the right slab thickness?
No. It estimates quantity from the thickness you enter. Driveways, patios, garage floors, and structural work can have different base, reinforcement, and local code requirements.
Does the cost include labor, base, forms, or delivery?
The main calculator's ready-mix cost is only cubic yards multiplied by your local price per cubic yard or cubic meter. The driveway planner can also price the concrete, base stone, rebar, forms, and stakes when you enter all five local material prices. Labor, delivery, short-load fees, finishing, and removal remain separate.
Can I calculate round footings, tubes, curbs, or steps here?
Yes. Choose the project type in the calculator. Slabs, round tubes, and curb sections include a quantity field; round footing mode supports a diameter, depth, and count; curb mode supports curb depth, height, length, quantity, and an optional gutter pan; and steps include run, rise, platform depth, width, and number of steps.
How does the concrete steps mode estimate volume?
It uses width × rise × [platform depth × steps + run × steps × (steps − 1) ÷ 2], with unit conversion and waste applied afterward. That is useful for quantity planning, but it is not a structural stair design or a substitute for an approved section drawing.