Concrete Calculator
Calculate the amount of concrete needed for your construction project. Get accurate estimates for volume, bags required, material costs, and raw materials for slabs, footings, columns, and stairs.
Concrete Calculator
How to Use the Concrete Calculator
- Choose Unit System: Select between Imperial (feet/inches) or Metric (meters/cm) measurements
- Select Shape: Choose from slab, footing, column, or stairs based on your project
- Enter Dimensions: Input the required measurements for your selected shape
- Set Waste Percentage: Add 5-15% waste depending on your experience level
- Review Results: See volume required, bags needed, and estimated costs
- Plan Materials: Use the raw materials breakdown for mixing your own concrete
Concrete Project Types
Slabs & Driveways
Typical thickness: 4-6 inches for cars, 6-8 inches for heavy vehicles
Standard thickness: 4-6 inches with reinforcement
Typical thickness: 3-4 inches for pedestrian traffic
Footings & Foundations
For walls and continuous foundations
Square or rectangular footings for columns
Basement and crawl space walls
Concrete Tips & Guidelines
Ordering Guidelines
- Waste Factor: Add 5-10% for experienced workers, 10-15% for DIY projects
- Delivery Time: Plan to pour concrete within 90 minutes of mixing
- Minimum Order: Most suppliers have a 1-3 cubic yard minimum
- Access: Ensure truck can reach within 150 feet of pour site
Mix Strength Guide
Calculation Examples
Example 1: Driveway Slab
Example 2: Foundation Footing
Frequently Asked Questions
How much concrete do I need for a 20x20 slab?
For a 20x20 foot slab that's 4 inches thick, you'll need approximately 4.94 cubic yards of concrete. With 10% waste factor, order about 5.5 cubic yards or 330 bags of 80lb concrete mix.
Should I buy bagged concrete or ready-mix?
Ready-mix is more convenient and cost-effective for large projects (over 2 cubic yards). Bagged concrete works well for small projects under 1 cubic yard. Consider your physical ability to mix and the time constraints of your project.
How much waste should I add to my calculation?
Add 5-10% waste for experienced contractors, 10-15% for DIY projects. Factors affecting waste include: complex shapes, inexperience, spillage during transport, and over-excavation of the area.
What's the difference between concrete strength ratings?
Concrete strength is measured in PSI (pounds per square inch). 3000 PSI is suitable for sidewalks and driveways, 3500 PSI for footings and foundation walls, and 4000+ PSI for heavy-duty commercial applications.
How long does concrete take to cure?
Concrete reaches about 70% strength in 7 days and 90% in 28 days. You can typically walk on it after 24-48 hours and drive on it after 7 days, depending on conditions and thickness.
Can I pour concrete in cold weather?
Concrete can be poured in temperatures as low as 40°F, but special precautions are needed. Below freezing, use heated water, additives, and insulation. Hot weather (above 90°F) also requires special care to prevent rapid drying.
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