Concrete Calculator

Calculate how much concrete you need for slabs, footings, columns, and stairs. Get results in cubic yards, cubic meters, and bags needed. Includes automatic 10% waste factor and cost estimates. Perfect for contractors and DIY projects.

Tip: Results include a 10% waste factor. Always order slightly more concrete than calculated to account for spillage and uneven ground.

Typical: 4 inches (10cm) for slabs

Optional - for cost estimate

How It Works

1. Choose Your Shape

Select the type of concrete work: Slab/Floor for driveways and patios, Footing/Wall for foundations, Column/Pier for posts, or Stairs for steps.

2. Enter Dimensions

Input the measurements for your project. Use feet and inches for imperial, or meters and centimeters for metric. Different shapes require different measurements.

3. Add Price (Optional)

Enter the price per cubic yard from your local supplier to get a cost estimate. This helps with budgeting your project.

4. Get Your Results

See how much concrete you need in cubic yards and cubic meters, number of bags for small jobs, and estimated total cost. Results include 10% waste factor.

Examples

Example 1: Concrete Slab (Patio)

Shape: Slab/Floor Length: 12 feet Width: 10 feet Thickness: 4 inches Price: $150/cubic yard Results: Concrete Needed: 1.63 cubic yards Pre-Mixed Bags: 244 (80lb) or 326 (60lb) Estimated Cost: $245 A 12x10 foot patio with standard 4-inch thickness. For this size, ready-mix delivery is more economical than bags.

Example 2: Concrete Footing

Shape: Footing/Wall Length: 20 feet Width: 12 inches Depth: 8 inches Price: $140/cubic yard Results: Concrete Needed: 0.81 cubic yards Pre-Mixed Bags: 121 (80lb) or 161 (60lb) Estimated Cost: $113 Foundation footing for a small structure. Could use bags or ready-mix depending on access.

Example 3: Concrete Columns

Shape: Column/Pier Diameter: 10 inches (Sonotube) Height: 4 feet Quantity: 6 piers Price: $150/cubic yard Results (per pier): Concrete Needed: 0.11 cubic yards For 6 piers: 0.66 cubic yards total Pre-Mixed Bags: ~99 (80lb) total Estimated Cost: $99 for all 6 Deck support piers. Small enough that bags might be easier than ordering ready-mix.

Frequently Asked Questions

How do I measure for a concrete slab?

Measure the length and width of the area in feet (or meters). For thickness, measure in inches (or centimeters). Standard slab thickness is 4 inches for patios and walkways, 6 inches for driveways. Multiply length × width × thickness, then convert to cubic yards by dividing by 27 for imperial (length and width in feet, thickness converted to feet).

Should I use bags or ready-mix concrete?

Use pre-mixed bags (60lb or 80lb) for small jobs under 1 cubic yard - easier for DIY projects and areas difficult for trucks to access. Use ready-mix concrete from a truck for jobs over 1 cubic yard - more economical, faster, and better quality mixing. The break-even point is typically around 1-1.5 cubic yards.

Why is there a 10% waste factor?

The 10% waste factor accounts for spillage during pouring, uneven subgrade (ground may not be perfectly level), over-excavation, and concrete lost in the chute/mixer. It is better to have slightly too much concrete than to run short during a pour, as you cannot easily stop and restart concrete work.

How thick should my concrete slab be?

Patios and walkways: 4 inches thick. Driveways and garage floors: 4-6 inches (6 inches for heavy vehicles). Basement floors: 4 inches over gravel base. Commercial/industrial: 6-8 inches or more. Always check local building codes and consider soil conditions and intended use.

How much does concrete cost per cubic yard?

Ready-mix concrete typically costs $100-$200 per cubic yard depending on your location, concrete strength (PSI), and distance from the plant. Special mixes (colored, fiber-reinforced, high-strength) cost more. Delivery fees may apply for small loads under 5 cubic yards. Always get quotes from local suppliers.