Concrete Calculator

Calculate how much concrete you need for slabs, footings, columns, and walls. Get volume in cubic yards, pre-mix bag counts (50, 60, 80 lb), weight, and cost estimate. Supports rectangular, cylindrical, and footing shapes.

🧱 Concrete Calculator

Volume

Cubic Feet33.33 cu ft
Cubic Yards1.23 cu yd
Cubic Meters0.9439 mΒ³

Pre-Mix Bags

50 lb Bags89 bags
60 lb Bags75 bags
80 lb Bags56 bags

Weight & Cost

Concrete Weight5,000.00 lbs

πŸ’‘ How to Calculate Concrete Volume

Concrete is ordered in cubic yards in the United States. For a rectangular slab, the formula is Length Γ— Width Γ— Depth β€” but the critical step most people miss is converting depth from inches to feet first. A 4-inch slab is 4 Γ· 12 = 0.333 feet, not 4 feet. Mixing up this unit conversion is the #1 reason homeowners over-order concrete.

For cylindrical shapes (sono tubes, columns, piers), use Ο€ Γ— radiusΒ² Γ— height. For pre-mix bags: a 50 lb bag fills about 0.375 cu ft, a 60 lb bag fills about 0.45 cu ft, and an 80 lb bag fills about 0.6 cu ft. For projects over 1 cubic yard, ordering a ready-mix truck is more economical and produces better results than hand-mixing individual bags.

Calculate volume with our cubic yards calculator. Measure your pour area with our square footage calculator. For block walls, see our concrete block calculator.

What Is Concrete?

Concrete is a composite material made by mixing Portland cement, water, sand (fine aggregate), and gravel or crushed stone (coarse aggregate). When water is added to the dry ingredients, a chemical reaction called hydration hardens the mixture into a durable, stone-like material.

Concrete is not the same as cement β€” cement is just one ingredient in concrete (typically 10–15% of the mix by volume). In the US, concrete is used for foundations, driveways, patios, sidewalks, retaining walls, curbs, columns, and footings.

Concrete is available in two forms: ready-mix (delivered by truck in large volumes) and pre-mixed bags (50, 60, or 80 lb bags that you mix with water on site). Ready-mix is standard for projects over 1 cubic yard.

Step-by-Step: How to Calculate Concrete

  1. Measure length and width of the pour area in feet. For irregular shapes, break the project into simple rectangles or cylinders and calculate each separately.
  2. Measure depth (thickness) in inches. Standard slab thicknesses: 4 inches for sidewalks and patios, 4–6 inches for residential driveways, 6–8 inches for commercial or heavy-load areas.
  3. Convert depth to feet: divide inches by 12. Example: 4 inches Γ· 12 = 0.333 feet.
  4. Calculate cubic feet: Length (ft) Γ— Width (ft) Γ— Depth (ft) = volume in cubic feet.
  5. Convert to cubic yards: divide cubic feet by 27. One cubic yard = 27 cubic feet = 3 ft Γ— 3 ft Γ— 3 ft.
  6. Add 5–10% extra for waste, spillage, uneven subgrade, and over-excavation. Running short during a pour creates a cold joint β€” which permanently weakens the concrete.

Concrete Volume Formulas

ShapeFormulaExample
Slab / RectangleL Γ— W Γ— D (all in feet)10 Γ— 10 Γ— 0.333 = 33.3 cu ft = 1.23 cu yd
Cylinder / ColumnΟ€ Γ— rΒ² Γ— H (all in feet)Ο€ Γ— 0.5Β² Γ— 4 = 3.14 cu ft = 0.12 cu yd
Footing / WallL Γ— W Γ— D (all in feet)40 Γ— 1.5 Γ— 1 = 60 cu ft = 2.22 cu yd
StairsBreak into steps + platformUse our concrete stairs calculator

How Many Bags of Concrete Per Cubic Yard?

For small projects, pre-mixed bags are convenient. Here's how many bags you need per cubic yard:

Bag SizeYield per BagBags per Cubic YardBags per Cubic Foot
50 lb0.375 cu ft72 bags2.67 bags
60 lb0.45 cu ft60 bags2.22 bags
80 lb0.6 cu ft45 bags1.67 bags

Tip: At more than 40–50 bags, consider ordering ready-mix instead. Hand-mixing that many bags is extremely labor-intensive and the quality may not be as consistent as truck-delivered concrete.

Concrete Coverage Table

How much area does one cubic yard of concrete cover at different thicknesses?

Slab ThicknessCoverage per Cubic Yard
2 inches162 sq ft
3 inches108 sq ft
4 inches81 sq ft
5 inches64.8 sq ft
6 inches54 sq ft
8 inches40.5 sq ft
12 inches (1 ft)27 sq ft

Concrete Cost (2025 US Pricing)

Cost ComponentTypical Range
Ready-mix per cubic yard$125–$165 delivered
Short-load fee (<5 yards)$50–$100 extra
50 lb pre-mix bag$4–$6 each
60 lb pre-mix bag$5–$7 each
80 lb pre-mix bag$6–$9 each
Installed (material + labor)$6–$20 per sq ft
Average 10Γ—10 patio (4")$750–$1,500 installed
Average 2-car driveway (20Γ—20, 5")$3,000–$6,000 installed

Factors affecting cost: concrete mix design (standard vs high-strength), delivery distance, pump truck (if needed for hard-to-reach areas), finishing style (broom, stamped, exposed aggregate), and your region. Saturday deliveries and orders under 5 yards often incur surcharges.

Tips for a Successful Concrete Pour

  • Build forms first: Use 2Γ—4 or 2Γ—6 lumber stakes to create the edges of your slab. Level the tops β€” they define the finished surface. Oil the inside face so forms release cleanly.
  • Prepare the base: Compact the subgrade, then add 4–6 inches of compacted gravel or crushed stone as a base. This prevents settling and improves drainage beneath the slab.
  • Add reinforcement: Use #3 or #4 rebar on 12–18 inch centers, or 6Γ—6 welded wire mesh (WWM), to prevent cracking. Support rebar on chairs so it sits in the middle third of the slab.
  • Order 5–10% extra: Subgrade is never perfectly level, forms may bow slightly, and some concrete is always lost to spillage and residue in the truck chute.
  • Have your crew ready: Concrete starts setting within 60–90 minutes. The truck, tools (screed, bull float, edger, broom), and all workers must be on site before the truck arrives.
  • Cure properly: Keep the surface moist for at least 7 days after pouring. Use curing compound, wet burlap, or plastic sheeting. Proper curing increases strength by 50% compared to uncured concrete.

Concrete Types & Mix Designs

TypePSI RatingCommon Uses
Standard Mix2,500–3,000 PSISidewalks, patios, non-structural slabs
High-Strength4,000–5,000 PSIDriveways, garage floors, footings, structural
Fiber-Reinforced3,000–4,000 PSISlabs where wire mesh is impractical; reduces surface cracking
Air-Entrained3,000–4,000 PSIRequired in freeze-thaw climates (northern US); tiny air bubbles absorb expansion
Fast-Setting4,000 PSI (1 day)Post setting, small repairs, cold-weather pours
A 10 Γ— 10 ft patio slab at 4 inches thick = 10 Γ— 10 Γ— 0.333 = 33.3 cu ft = 1.23 cubic yards = about 89 bags (50 lb), 74 bags (60 lb), or 56 bags (80 lb). At $140/yard, that's about $172.

Concrete Calculator FAQ

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