Concrete Calculator
Calculate concrete volume, material quantities, and costs for slabs, columns, footings, stairs, and more. Get accurate estimates for cement, sand, gravel, water, and delivery.
Unit System
Shape
Slab Dimensions
Number of identical shapes to pour (e.g., multiple columns)
Recommended: 5-10% for most projects
Concrete Mix
Cost Estimation (Optional)
Rebar Calculator (Optional)
Distance between rebar (typical: 12-18 inches)
Enter dimensions above to calculate concrete volume and material quantities
Table of Contents
What is Concrete?
Concrete is one of the most widely used construction materials in the world. It's a composite material made from a mixture of:
- Cement: A binding agent that hardens when mixed with water (typically Portland cement)
- Sand: Fine aggregate that fills spaces between larger particles
- Gravel/Aggregate: Coarse aggregate that provides strength and bulk
- Water: Activates the cement and allows the mixture to be workable
When mixed in the correct proportions, concrete forms a strong, durable material that's ideal for foundations, slabs, columns, and many other structural elements. The key to successful concrete projects is calculating the correct volume needed and ordering the right amount of materials.
Why use a concrete calculator? Accurately estimating concrete volume prevents wasteful over-ordering (costly) or dangerous under-ordering (project delays). This calculator helps you determine exactly how much concrete you need for your project, including recommended waste factors for spillage and uneven surfaces.
How it Works
Our concrete calculator performs comprehensive calculations based on your project specifications:
- Select Shape: Choose from slab, column (round or square), footings, stairs, curb/gutter, or enter a custom volume
- Enter Dimensions: Input length, width, height/depth in your preferred unit system (Imperial or Metric)
- Set Parameters: Specify quantity (for multiple identical pours), waste factor (typically 5-10%), and concrete mix ratio
- Calculate: The calculator automatically computes:
- Volume in cubic yards, cubic meters, and cubic feet
- Number of concrete bags needed (60lb, 80lb, or 90lb options)
- Material breakdown (cement, sand, gravel, water)
- Cost estimates (if prices are provided)
- Rebar requirements (for slabs)
- Formwork square footage
- Number of concrete truck loads needed
All calculations include the waste factor to ensure you order enough material. The calculator supports both ready-mix concrete (ordered by cubic yard) and bagged concrete mixes.
Supported Shapes
Slab (Rectangular)
The most common concrete shape. Used for driveways, patios, floors, and foundations.
Volume = Length × Width × Depth
Example: A 20 ft × 10 ft × 0.33 ft (4 inch) slab = 66 cubic feet = 2.44 cubic yards
Column (Circular)
Round columns for structural support. Common in commercial and residential construction.
Volume = π × (Diameter/2)² × Height
Example: A 2 ft diameter × 10 ft height column = 31.4 cubic feet = 1.16 cubic yards
Column (Square)
Square columns, common in residential and light commercial construction.
Volume = Side × Side × Height
Example: A 1.5 ft × 1.5 ft × 10 ft column = 22.5 cubic feet = 0.83 cubic yards
Footings
Foundation footings that distribute building loads to the soil. Typically wider than they are deep.
Volume = Length × Width × Depth
Example: A 20 ft × 2 ft × 1 ft footing = 40 cubic feet = 1.48 cubic yards
Stairs
Concrete stairs. Calculated using tread (horizontal), riser (vertical), width, and number of steps.
Volume = (Tread × Riser × Width) / 2 × Number of Steps
Example: 10 steps with 11 in tread, 7 in riser, 4 ft width ≈ 12.8 cubic feet = 0.47 cubic yards
Curb/Gutter
Linear concrete elements for road edges and drainage. Rectangular cross-section.
Volume = Width × Height × Length
Example: 6 in × 18 in × 100 ft curb = 75 cubic feet = 2.78 cubic yards
Custom
Enter a custom volume directly if your shape doesn't fit the standard options. Useful for complex geometries or when you've already calculated the volume elsewhere.
Concrete Mix Ratios
Concrete mix ratios specify the proportions of cement, sand, and gravel (aggregate). Different mixes are suitable for different applications:
1:2:3 Mix (Standard)
Composition: 1 part cement : 2 parts sand : 3 parts gravel
Best for: General-purpose concrete work, driveways, patios, foundations, slabs. Provides good strength (typically 3000-4000 PSI) and workability.
Strength: Medium-high strength, suitable for most residential and light commercial projects.
1:3:3 Mix (Rich Mix)
Composition: 1 part cement : 3 parts sand : 3 parts gravel
Best for: Higher strength requirements, structural elements, columns, beams. This mix uses more cement for increased strength.
Strength: High strength (typically 4000-5000 PSI), better for load-bearing applications.
Custom Mix
Create your own mix ratio by specifying the proportions of cement, sand, and gravel. Use this for specialized applications or when following specific engineering specifications.
Bag Sizes: Ready-mix concrete bags come in 60 lb, 80 lb, and 90 lb sizes. 80 lb bags are the most common and recommended for most projects. Larger bags are more economical but harder to handle.
Examples
Example 1: Driveway Slab
Project: Pour a 24 ft × 12 ft driveway that's 6 inches (0.5 ft) deep
Calculation: 24 × 12 × 0.5 = 144 cubic feet = 5.33 cubic yards
With 5% waste: 5.33 × 1.05 = 5.6 cubic yards
Bags needed: ~84 bags (80 lb bags) or 1 ready-mix truck (typically 10 cubic yards)
Example 2: Foundation Footings
Project: Pour 4 footings, each 2 ft × 2 ft × 1.5 ft deep
Per footing: 2 × 2 × 1.5 = 6 cubic feet = 0.22 cubic yards
Total (4 footings): 0.22 × 4 = 0.88 cubic yards
With 10% waste: 0.88 × 1.10 = 0.97 cubic yards ≈ 15 bags (80 lb)
Example 3: Round Column
Project: Pour a 18-inch (1.5 ft) diameter column that's 10 ft tall
Calculation: π × (1.5/2)² × 10 = π × 0.5625 × 10 = 17.67 cubic feet = 0.65 cubic yards
With 5% waste: 0.65 × 1.05 = 0.68 cubic yards ≈ 10 bags (80 lb)
Common Use Cases
- Residential Construction: Calculate concrete for driveways, patios, sidewalks, foundations, and garage floors
- Commercial Projects: Estimate materials for large slabs, parking lots, and structural elements
- Foundation Work: Calculate concrete needed for footings, stem walls, and foundation walls
- Structural Elements: Determine material quantities for columns, beams, and load-bearing walls
- Road and Infrastructure: Calculate concrete for curbs, gutters, sidewalks, and roadways
- DIY Projects: Plan small-scale projects like stepping stones, garden borders, and decorative elements
- Cost Estimation: Budget projects by calculating material and delivery costs
- Material Ordering: Determine how many bags or truck loads to order from suppliers
- Project Planning: Plan concrete pours and schedule delivery trucks appropriately
- Waste Minimization: Optimize orders to reduce waste and excess material costs
Frequently Asked Questions
Enter your project dimensions (length, width, depth) and select the appropriate shape. The calculator will automatically compute the volume in cubic yards, cubic meters, and cubic feet. Always add a 5-10% waste factor to account for spillage, uneven surfaces, and measurement variations.
Most projects use a 5-10% waste factor. Smaller projects or complex shapes may require 10-15%. The waste factor accounts for spillage during pouring, uneven surfaces, formwork irregularities, and measurement errors. It's better to order slightly more than run short mid-pour.
Approximately 45 bags of 80 lb concrete or 60 bags of 60 lb concrete equal one cubic yard. However, the exact number depends on the mix design and moisture content. For large projects (over 2-3 cubic yards), ready-mix concrete delivered by truck is usually more economical than bags.
Ready-mix concrete is delivered by truck, usually in 10-cubic-yard loads, and is mixed on-site or at the plant. It's best for larger projects. Bagged concrete comes in 60 lb, 80 lb, or 90 lb bags that you mix yourself with water. Bags are better for smaller projects, repairs, or hard-to-reach areas where trucks can't go.
The 1:2:3 mix (1 part cement : 2 parts sand : 3 parts gravel) is the standard for most projects like driveways, patios, and foundations. The 1:3:3 mix (rich mix) provides higher strength for structural elements like columns and beams. Follow your project's engineering specifications if available.
Enter the tread (horizontal depth), riser (vertical height), width of the stairs, and number of steps. The calculator uses a triangular approximation to estimate the volume per step, then multiplies by the number of steps. For more accurate calculations on complex stair designs, consider breaking them into separate sections.
Concrete prices vary by location, but typically range from $100-$200 per cubic yard for ready-mix concrete. Factors affecting price include strength requirements, additives, delivery distance, and local market conditions. Always get quotes from local suppliers for accurate pricing.
Standard concrete trucks carry approximately 10 cubic yards. The calculator divides your total volume (including waste factor) by 10 to determine the number of truck loads needed. Some suppliers offer smaller trucks (6-7 cubic yards) or larger trucks (11-12 cubic yards), so confirm with your supplier.
For slab calculations, enter the slab area (length × width) and rebar spacing (typically 12-18 inches). The calculator estimates the total length of rebar needed. Rebar requirements depend on load requirements and local building codes, so consult with a structural engineer for critical projects.
Formwork (or forms) are temporary structures that hold wet concrete in place until it hardens. The calculator estimates the square footage of formwork needed based on the perimeter and depth of your concrete pour. Formwork requirements vary by shape - slabs need perimeter forms, while columns need forms around all sides.
Yes! The calculator supports both Imperial (feet/inches) and Metric (meters/centimeters) units. Simply toggle the unit system at the top of the calculator. All results are displayed in both systems for easy reference, regardless of your input units.
The calculator provides accurate estimates based on standard concrete mix proportions and industry averages. However, actual material requirements may vary slightly based on specific mix designs, aggregate density, moisture content, and compaction methods. Use these calculations as estimates and consult with your concrete supplier for final quantities.
Calculate each shape separately, then add the volumes together. For example, if you're pouring a foundation with footings and walls, calculate the footings volume and wall volume separately, then sum them. You can also use the "Quantity" field to calculate multiple identical shapes at once.