Concrete Calculator
Calculate how much concrete you need for slabs, footings, columns, and walls. Enter your project dimensions and choose between bulk cubic yards or bagged concrete for instant results.
Quick Answer: How Much Concrete Do I Need?
For a standard 4-inch thick concrete slab:
Formula:
(Length × Width × Depth) ÷ 12 ÷ 27 = Cubic Yards
Depth in inches, divide by 12 for feet, then by 27 for cubic yards
Example:
10ft × 10ft × 4in slab:
(10×10×4)÷12÷27 = 1.23 cubic yards
Use calculator below for your specific project dimensions.
When to Use This Concrete Calculator
✅ Perfect For
- DIY projects - Patios, sidewalks, shed floors
- Home construction - Footings, slabs, foundations
- Landscaping - Retaining walls, garden borders
- Small contractors - Quick material estimation
- Educational use - Learning concrete calculations
⚠️ Professional Projects
- Commercial construction - Consult structural engineer
- Building code compliance - Verify local requirements
- Complex geometries - Irregular shapes need advanced tools
- Large volumes - >10 cubic yards, get professional quote
- Special mixes - High-strength, fiber-reinforced, etc.
Safety note: Always order 5-10% extra concrete to account for spillage and variations.
How to Calculate Concrete
The concrete volume formula converts your project dimensions into cubic yards:
- Measure the area you want to pour in feet (length and width).
- Determine the thickness in inches. Standard slabs are 4 inches thick.
- Calculate volume: Length (ft) × Width (ft) × Depth (in) ÷ 12 ÷ 27 = Cubic Yards.
- Convert to bags: Divide cubic yards by the yield per bag to get the number of bags needed.
Concrete Thickness Guide
- 4 inches: Sidewalks, patios, shed floors, and standard slabs
- 6 inches: Driveways, garage floors, and areas with vehicle traffic
- 8 inches: Foundation walls and structural elements
- 12 inches: Footings, load-bearing foundations, and columns
Concrete Types and Uses
- Standard mix (2,500 PSI): General-purpose use for walkways and patios
- Crack-resistant (4,000 PSI): Driveways and garage floors
- High-strength (5,000+ PSI): Footings, foundations, and structural work
- Fast-setting: Post holes, small repairs, and cold-weather pours
Frequently Asked Questions
How much concrete do I need?
To calculate concrete needed: multiply length × width (in feet) × depth (in inches), divide by 12 to convert to feet, then divide by 27 to get cubic yards. For example, a 10ft × 10ft slab at 4 inches deep needs about 1.23 cubic yards of concrete.
How many bags of concrete for a 10x10 slab?
A 10×10 foot slab at 4 inches thick requires approximately 1.23 cubic yards of concrete. That equals about 56 bags of 80lb concrete mix, 72 bags of 60lb mix, or 112 bags of 40lb mix. For slabs this size, ordering ready-mix concrete is often more practical.
How much does concrete cost per yard?
Ready-mix concrete typically costs $125-$165 per cubic yard delivered, depending on your location and the mix type. Bagged concrete costs more per yard — roughly $250-$350 per cubic yard when buying 80lb bags. For projects over 1 cubic yard, ready-mix is usually more economical.
How thick should a concrete slab be?
Standard concrete slab thickness: 4 inches for patios, sidewalks, and shed floors; 6 inches for driveways and garage floors; 8-12 inches for footings and structural foundations. Always check local building codes for minimum requirements.
How long does concrete take to cure?
Concrete typically takes about 24-48 hours to set enough to walk on, 7 days to reach 70% of its strength, and 28 days to fully cure. Temperature, humidity, and mix design can affect curing time. Keep concrete moist during curing for optimal strength.
Can I use this calculator for footings and columns?
Yes, you can use this calculator for footings and columns by entering the appropriate dimensions. However, we also have dedicated calculators for concrete footing and concrete column that may provide more specific guidance for those applications. For footings, use our concrete footing calculator, and for columns, use our concrete column calculator.
What is the formula to calculate concrete volume?
The basic formula is Length (ft) × Width (ft) × Depth (in) ÷ 12 = Volume (cubic feet). To convert to cubic yards, divide the cubic feet by 27. For example, a 20ft by 10ft slab at 6 inches deep is (20 × 10 × 6) / 12 = 100 cubic feet. 100 / 27 ≈ 3.7 cubic yards.
How do I calculate concrete for a round column?
For a cylindrical column, use the formula: π × (radius in feet)² × height in feet. π is approximately 3.1416. First, convert the diameter to radius (divide by 2). For a column with a 2-foot diameter (1-foot radius) and 10 feet tall: 3.1416 × (1)² × 10 = 31.416 cubic feet. Divide by 27 to get about 1.16 cubic yards.
Should I order extra concrete, and how much?
Yes, it's standard practice to order 5-10% extra concrete to account for spillage, over-excavation, and slight variations in subgrade. For a project calculated at 4 cubic yards, ordering 4.2 to 4.4 cubic yards is recommended. It's better to have a little extra than to run short.
Project Materials and Cost Estimate
Here's a breakdown of typical materials and costs for common concrete projects:
| Project Type | Concrete (yd³) | Rebar/Wire Mesh | Formwork | Gravel Base | Total Cost Range |
|---|---|---|---|---|---|
| 10x10 ft Slab (4" thick) Patio, sidewalk, shed floor |
1.23 yd³ | Wire mesh 100 sq ft | 40 linear ft (2×4) | 0.82 yd³ | $450 - $650 |
| 20x30 ft Driveway (6" thick) Two-car driveway with vehicle traffic |
11.11 yd³ | Rebar grid (18" spacing) | 100 linear ft (2×6) | 4.12 yd³ | $3,500 - $5,000 |
| Foundation Footings (12"x12") For 24x36 ft building |
4.44 yd³ | #5 rebar continuous | 2×8 lumber + stakes | Not required | $1,800 - $2,500 |
| Concrete Retaining Wall 20 ft long × 4 ft high × 8" thick |
3.95 yd³ | Vertical/horizontal rebar | Plywood forms + braces | Gravel backfill | $2,200 - $3,200 |
Material Price Reference (Approximate)
- Ready-mix concrete: $125 - $165 per cubic yard (delivered)
- Bagged concrete (80lb): $5 - $7 per bag ($250 - $350 per yd³)
- Rebar (#4, 20 ft): $9 - $13 per piece
- Wire mesh (6×6 inch): $0.40 - $0.55 per sq ft
- Gravel base (3/4" crushed): $40 - $60 per cubic yard
- Form lumber (2×4): $2.50 - $4.00 per linear foot
Note: Costs are approximate and vary based on location, material availability, project complexity, and labor. Professional installation typically adds $5-$15 per square foot for slabs and $20-$40 per square foot for complex foundations/walls. Always obtain multiple quotes for your specific project.