Concrete Calculator
Estimate cubic yards of concrete needed
How to Use the Concrete Calculator
Our concrete calculator helps you estimate the amount of concrete needed for your construction project, whether you're pouring a patio, driveway, foundation, or column footings. Simply enter your dimensions and get instant results in cubic yards, along with the number of pre-mixed bags you'll need.
Understanding the Formula
For rectangular slabs, we calculate volume using: Length × Width × Depth. For circular columns, we use: π × radius² × depth. The result is converted from cubic feet to cubic yards by dividing by 27. Need to calculate the area first? Use our square footage calculator to determine your slab dimensions.
Tips for Accurate Results
- Always add 10-15% extra for waste and uneven surfaces
- Measure depth in inches for more precise calculations
- For irregularly shaped areas, break them into rectangles and add the results
- Consider the weight capacity of your vehicle if picking up bags
Related Projects
Planning a larger construction project? You may also need to calculate gravel for your base layer, lumber for forms, or roofing materials for an attached structure. For a comprehensive guide on concrete projects, read our Complete Guide to Concrete Projects.
When to Consult a Professional
For structural applications like foundations, load-bearing walls, or any project requiring reinforcement, always consult with a structural engineer or licensed contractor. They can ensure proper mix design, reinforcement placement, and curing procedures.
Frequently Asked Questions
For a 10x10 foot slab at 4 inches thick, you need approximately 1.23 cubic yards of concrete. This translates to about 56 bags of 80-pound concrete mix or 74 bags of 60-pound mix. We recommend adding 10% extra for waste and uneven ground.
A standard concrete patio should be 4 inches thick for foot traffic only. For areas that will support light vehicles or heavy furniture, increase thickness to 5-6 inches. Always pour over a compacted gravel base of 4-6 inches for proper drainage and stability.
Multiply length (ft) x width (ft) x depth (ft), then divide by 27 to convert cubic feet to cubic yards. For example, a 12x12 foot area at 4 inches (0.33 ft) deep equals 12 x 12 x 0.33 / 27 = 1.76 cubic yards.
Concrete reaches about 70% of its strength in 7 days and full strength in 28 days. You can walk on it after 24-48 hours, drive on it after 7 days, but avoid heavy loads for at least 28 days. Keep it moist during the first week for optimal curing.
Cement is just one ingredient in concrete. Concrete is made by mixing cement (the binding agent) with water, sand (fine aggregate), and gravel or crushed stone (coarse aggregate). Cement typically makes up 10-15% of the concrete mix by volume.
Ready-mix concrete typically costs $120-$150 per cubic yard for delivery, depending on your location and mix type. Bagged concrete costs more per yard but is practical for small projects. For slabs larger than 1 cubic yard, delivery is usually more economical.
Concrete can be poured in cold weather but requires precautions. Below 50 degrees F, concrete sets slower. Below 40 degrees F, you need heated enclosures or insulating blankets. Never pour on frozen ground, and use hot water in the mix to maintain temperature.