Concrete Calculator
Calculate concrete slab volume in cubic meters. Length, width, depth inputs.
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Examples to try
Volume
Volume ≈ length × width × depth (convert depth cm → m first). Order a little extra for waste.
Common mistakes
- Leaving depth in cm while length/width are meters without converting.
- Forgetting waste factor (often 5–10%).
- Ignoring rebar, slope, or irregular shapes.
Scope: Rectangular volume estimate only — not a structural design tool.
How to Use
Enter your values in the fields above and click Calculate to get instant results. All computations run locally in your browser. No data is ever uploaded or stored.
Related Calculators
Concrete Volume Estimation
CalcSolver computes the volume of your pour in cubic meters (or cubic feet) by multiplying length × width × depth. For a rectangular slab, this is a direct three-dimensional product.
Volume (m) = length(m) × width(m) × depth(m)
Order quantity = volume × 1.10 (add 10% waste factor)
Common Project Volume Estimates
10 × 10 ft slab, 4 in deep: ~1.23 yd³ (order 1.35 with waste)
Driveway 20 × 30 ft, 5 in: ~9.25 yd³ (order 10.2)
Sonotube 12 in diameter × 4 ft: ~0.42 yd³ each
Ready-mix price: $120–$180/yd³ (varies by region), plus delivery for small loads
Concrete Volume Estimation
CalcSolver's concrete calculator estimates the volume of concrete needed for rectangular slabs, circular columns, and footings. Accurate volume estimation prevents costly over-ordering or project-delaying shortages. Whether you are pouring a backyard patio or a commercial foundation, getting the math right the first time saves both time and money.
Volume Formulas
The basic formula for concrete volume is Length x Width x Depth. For a rectangular slab, multiply all three dimensions in the same units. Convert the result to cubic yards (divide cubic feet by 27) or cubic meters as needed. For circular columns, use V = π x r² x height. For footings, multiply the perimeter of the structure by the footing width and depth. Always ensure all measurements use consistent units before calculating.
Converting Volume to Bags
When ordering pre-mixed bags instead of ready-mix delivery, you need to know the yield per bag. A 40-pound bag yields approximately 0.30 cubic feet. A 60-pound bag yields approximately 0.45 cubic feet. An 80-pound bag yields approximately 0.60 cubic feet. To find the number of bags, divide your total cubic footage by the per-bag yield. For example, a 10ft x 10ft slab at 4 inches deep requires 33.33 cubic feet, which means 56 bags at 80 pounds each (33.33 / 0.60 = 55.55, rounded up).
Waste Factor: Why Order Extra
Professional contractors always order 10-15% more concrete than the calculated volume. This accounts for spillage during delivery, uneven subgrade surfaces, form board imperfections, and minor measurement errors. For DIY projects, consider a 15% waste factor since inexperience tends to increase material loss. A project requiring 5 cubic yards should therefore order 5.5 to 5.75 yards. The cost of an extra half-yard is far less than the expense of a second delivery or a cold joint in your slab.
Types of Concrete
- Standard ready-mix (3,000-4,000 PSI): driveways, sidewalks, and general construction. The most common type for residential projects.
- High-strength mix (5,000-6,000 PSI): commercial floors, structural columns, and load-bearing applications.
- Self-leveling concrete: interior floors requiring a smooth, flat surface. Flows easily and settles evenly.
- Fiber-reinforced concrete: contains synthetic fibers for added crack resistance, reducing the need for wire mesh.
- Fast-setting concrete: sets in 20-40 minutes, ideal for posts, small repairs, and time-sensitive projects.
Real Project Examples
Example 1 — Patio slab: A 12ft x 16ft patio, 4 inches deep requires 12 x 16 x 0.333 = 63.94 cubic feet = 2.37 cubic yards. With 10% waste: 2.61 yards to order. At $140 per yard, budget approximately $365 for concrete alone.
Example 2 — Driveway: A 20ft x 24ft driveway, 6 inches deep requires 240 cubic feet = 8.89 cubic yards. With 15% waste: 10.22 yards. At $150 per yard with a $100 delivery fee, total cost is approximately $1,633.
Example 3 — Fence posts (10 holes): Each hole is 12 inches diameter and 36 inches deep. Volume per hole = π x 0.5² x 3 = 2.36 cubic feet. Total for 10 posts = 23.6 cubic feet = 40 bags of 80-pound mix.
Ordering Tips
- Ready-mix delivery is more economical for projects requiring more than 1 cubic yard.
- Schedule delivery for early morning to avoid heat-related setting issues in summer.
- Have all forms, tools, and helpers ready before the truck arrives — concrete waits for no one.
- For large pours, consider ordering in multiple smaller loads to manage working time.
- Ask about short-load fees — some companies charge extra for deliveries under a minimum volume.
Use CalcSolver's unit converter to switch between metric and imperial measurements, and the percentage calculator to quickly compute waste factors.
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Frequently Asked Questions
How do I calculate how much concrete I need?
Calculate the volume of your project: length × width × depth. Concrete is sold by the cubic yard. To convert cubic feet to cubic yards, divide by 27. Always order 5-10% extra to account for spillage and uneven surfaces.
What is the difference between concrete and cement?
Cement is an ingredient in concrete. Concrete is a mixture of cement, sand, gravel (aggregate), and water. Cement is the binding agent that holds the mixture together.
How many bags of concrete do I need?
A standard 80-pound bag of premixed concrete covers about 0.6 cubic feet. For a 4-inch thick slab that is 10 feet by 10 feet, you need about 37 bags (33.33 cubic feet ÷ 0.6).
Should I order ready-mix delivery or mix my own bags?
Ready-mix delivery is more economical and practical for projects over 1 cubic yard. Bag mixing is suitable for small jobs like fence posts or minor repairs. For a full driveway or patio, delivery saves significant time and labor.
How long does concrete take to cure?
Concrete sets within 24-48 hours but takes 28 days to reach full strength. Keep it moist during the first week by covering with plastic or spraying with water. Avoid heavy loads for at least 7 days and vehicular traffic for 28 days.
What is the difference between concrete and mortar?
Mortar uses cement and fine sand (no coarse aggregate) and is designed to bind bricks or blocks together. Concrete includes coarse aggregate (gravel) for structural strength and is used for slabs, foundations, and structural elements.