Concrete calculator for slabs, footings & beams
Enter each pour as its own line: slab, continuous footing, grade beam, pier. The calculator converts to cubic yards, rounds to an orderable quantity, and gives you the weight and the bag count if the job is small enough to mix.
- Slabs, footings, beams & piers
- Waste and order rounding
- Weight in pounds and tons
- Premix bag count
1 · Slabs, footings, walls & beams L × W × depth × qty
2 · Round piers & columns π × r² × height × qty
3 · Order & materials
Volume formulas are standard geometry. 1 yd³ = 27 ft³; 1 ft³ = 0.0283168 m³. Portland cement bag = 94 lb ≈ 1 ft³ (CMHA TEK 4-2A conversion note). Waste %, density, dry-volume factor and bag yield are editable assumptions.
Volume by element type
Live formula
Save your results
Copy these results, then add your approved sample files in the trial brief.
Read the result the way a concrete estimator would
The calculator is quick. The judgment is in what you feed it.
Concrete quantities go wrong in three predictable places: thickness, footing dimensions taken from the wrong detail, and waste applied twice. Each line in the calculator is a separate element so you can see which pour drives the order. A 4 in slab that is actually 4½ in at the thickened edges, or a footing detail that changed between the foundation plan and the sections, will show up as a line you can question instead of a number buried in a total.
- Slab on grade. Length × width × thickness. Add thickened edges and turndowns as their own beam lines; a perimeter thickening of 12 in × 12 in around a 100 × 60 ft slab adds about 12 yd³, which is easy to miss.
- Continuous footings. Take the length along the centerline of the wall, not the outside face, or you count the corners twice.
- Spread footings and piers. Count from the footing schedule, then check the count against the grid on the plan. Mark types that appear on the plan but not in the schedule.
- Beams and grade beams. Width × depth × length, deducting the slab if the beam is poured monolithically with it.
- Weight. Normal-weight concrete is about 150 lb/ft³ (≈4,050 lb/yd³). Use it for crane picks, precast checks and demo haul-off, not for ordering.
The math behind every line
Every result in the calculator comes from these conversions. They are also shown live under the result panel, using your own numbers.
| Element | Typical dimensions | Watch for |
|---|---|---|
| Slab on grade | 4 to 6 in thick | Thickened edges, depressed slabs, sloped areas |
| Continuous footing | 12 to 24 in wide | Steps, corners counted twice, pilaster bumps |
| Spread footing | per schedule | Types on plan missing from schedule |
| Pier / column | diameter × depth | Bell bottoms, over-excavation |
| Grade beam | width × depth | Monolithic pours with the slab |
Typical dimensions are general ranges to sanity-check entries, not design values. The drawings govern.
When the takeoff is the slow part
A calculator is only as good as the dimensions you typed into it. On a real foundation package, the slow part is finding every footing type, matching it to the schedule, and noticing when an addendum changes a depth. That is the part RenderDraw is built to speed up: the AI reads the plan set, pulls quantities from schedules and plan views, and flags anything it could not confirm so an estimator decides, not the software.
Concrete calculator price
Enter your ready-mix price per cubic yard and the calculator multiplies it by the order quantity after waste and rounding. That is the material price only; placing, pumping, forming, rebar and finishing are priced separately, which is why per-square-foot slab prices vary so much.
To get a material price per square foot of slab, divide the concrete cost by the slab area. At 4 in thick, one cubic yard covers 81 sq ft (324 ÷ 4); at 6 in, it covers 54 sq ft.
The concrete estimating formula
The same formula drives estimates for driveways, roads and footings; only the dimensions and the waste allowance change. Formwork is usually priced in SFCA, rebar in tons and finishing by square foot.
Concrete quantities from the drawings, not from memory.
RenderDraw's AI takeoff proposes slab areas, footing and wall runs, and schedule-driven counts from structural and civil sheets, keeps the source on each row, and holds uncertain items for review.
- Areas, lengths and counts with sources. Every quantity links to its sheet and location.
- Schedules read in context. Footing and pier schedules tied to plan marks.
- Addenda through the same review. Send the changed sheets back through takeoff and estimator review.
- Your mix, waste and labor. Pricing stays with your estimator.
Send one concrete set
Files stay private while RenderDraw assesses the request. No obligation.
RenderDraw does not publish accuracy percentages or time-saved claims. Test it on your own plan set.
Questions estimators ask.
How many cubic yards are in a 10 × 10 slab that is 4 inches thick?
10 × 10 × 4 ÷ 12 = 33.3 ft³, divided by 27 = 1.23 yd³. With 10% waste that is 1.36 yd³, so most suppliers would have you order 1.5 yd³.
How do I calculate concrete for footings?
Multiply footing width × depth × length for continuous footings (use centerline length), and width × length × depth × count for spread footings. Add each as its own line in the calculator so you can check them against the footing schedule.
How much does a cubic yard of concrete weigh?
Normal-weight concrete is about 150 lb per cubic foot, or roughly 4,050 lb per cubic yard. Lightweight mixes are lower; the density field is editable.
When should I use bags instead of ready-mix?
Bags make sense for small pours, such as setting posts or a small pad. At about 0.6 ft³ per 80 lb bag, one cubic yard is around 45 bags, which is the point where most crews call a truck.
Can this calculator replace a concrete takeoff?
No. It does the math for dimensions you already have. The takeoff is finding those dimensions on the drawings. RenderDraw can extract them from your plan set for review. Request a free sample takeoff.
What is the concrete estimating formula?
Cubic yards = length × width × depth in inches ÷ 12 ÷ 27, summed by element, plus waste and rounding to the supplier increment.
How do I calculate concrete price per square foot?
Divide the concrete cost by the slab area. One cubic yard covers 81 sq ft at 4 in thick, before waste.
Stop re-adding footing schedules by hand.
Send a foundation plan set. RenderDraw extracts the footing and slab quantities, flags what it could not read, and you check the numbers against this calculator.
- Upload the plans, specs and schedules, plus an addendum if you have one.
- RenderDraw reviews the set and the scope you want tested.
- We follow up with extracted quantities, flagged items and next steps.