Concrete
Concrete Slab Calculator
Calculate concrete volume for rectangular slabs. Get cubic yards, bags, and cost.
Inputs
Live estimate
Material needed
6.17 cu yd
- Area
- 500 sq ft
- Cubic feet
- 166.67
- Cubic yards
- 6.17
- Estimated tons
- 12.35 tons
- Estimated truckloads
- 0.62
- 80 lb bags
- 278
You will likely need
- •6.17 cu yd — material needed
- •Schedule 1 truck load
- •Approximate delivered weight: 12.35 tons
- •278 bags
Diagram
Live estimate
- Mathematical quantity
- 6.2 cu yd
- Placement contingency
- +5% → 6.5 cu yd
- Field conditions
- Not applied
- Adjusted requirement
- 6.5 cu yd
- Ordering rule
- Round up to nearest 0.5 cu yd
- Suggested order
- 6.5 cu yd
Small over-excavation, form deflection, and pump / handling loss during placement.
What you actually need in the field, before rounding to a supplier-friendly ordering unit.
Estimator confidence
HighSmall over-excavation, form deflection, and pump / handling loss during placement.
Improve confidence: Increase for pumped placements or complex forms.
Why this behavior applies: Concrete is a rigid, formed material. The only real adjustment is placement contingency — form deflection, small over-excavation, and pump / bucket loss.
- Sub-base flatness — A ½-in low spot across 100 sq ft is about ⅙ cu yd of extra concrete.
- Form deflection — Poorly braced forms bulge under load and drink additional yardage.
- Whether the pour is pumped — Pump primer and line loss add up to about ¼ cu yd.
- Verify thickened edges and over-excavation — a 4-inch slab with a 6-inch perimeter thickens the order.
- Confirm reinforcement (mesh, fiber, or rebar) before scheduling the pour.
- Have finishing crew and tools on-site before the truck arrives — pour times are unforgiving.
- Forgetting thickened perimeter edges when computing volume.
- Ignoring waste and ordering exactly the calculated volume.
- Skipping isolation and control joints on larger slabs.
Smart tips
- Ordering 5–10% extra is standard on irregular layouts. Running short costs more than the excess.
How it's calculated
Area is derived from your shape inputs and converted to sq ft.
Depth is converted to feet; cubic feet = area × depth.
Cubic yards = cubic feet ÷ 27, then × (1 + waste %) × (1 + compaction %).
Estimated tons = cubic yards (with waste) × 2.
Truckloads = cubic yards (with waste) ÷ truck capacity.
Total cost = cubic yards (with waste) × price per cubic yard + delivery.
Material assumptions
- Concrete density: 2.0 tons per cubic yard (~4,050 lb).
- Standard slab thickness: 4 inches; driveways: 5–6 inches.
- One 80 lb bag ≈ 0.022 cubic yards; ~45 bags per cubic yard.
Frequently asked questions
Related calculators
Related articles
Deeper guidance from the Learn library — sizing, depth, waste, and ordering for this material.
- How Much Concrete Do I Need?Concrete estimating comes down to volume, waste, and delivery format. Here's the math and the decision rule between bags and ready-mix.
- How to Calculate Cubic YardsA cubic yard is the standard unit for bulk material. Here's the formula and a worked example.
- How to Estimate Concrete for a SlabCubic yards = area × thickness ÷ 27. Add 10% waste. Over ~1 cubic yard, switch from bags to ready-mix.
These results are estimates only. Confirm quantities, compaction, waste, and delivery requirements with your supplier or project professional before ordering materials.