Concrete Slab
Estimate concrete volume in cubic yards, bags needed, total cost, and weight for any concrete slab. Free online construction calculator for contractors and DIYers.
About This Calculator
This free concrete slab calculator helps contractors, builders, and DIY homeowners estimate the exact amount of concrete needed for any slab project. Simply enter the slab length and width in feet and the depth in inches to get instant results for cubic yards, cubic feet, number of 60 lb bag equivalents, total material cost, and slab weight.
The calculator uses the standard formula: Volume (cubic feet) = Length (ft) × Width (ft) × Depth (in) ÷ 12. It then converts cubic feet to cubic yards (divide by 27), estimates the number of 60 lb bags needed (each bag yields approximately 0.45 cubic feet), calculates total cost based on bag price, and computes slab weight using concrete's density of 150 pounds per cubic foot.
Regional Notes
United States: Concrete is typically sold by the cubic yard with bagged mix available at home improvement stores. Standard 60 lb bags cost $4-7 and 80 lb bags cost $5-9. Ready-mix concrete costs $100-150 per cubic yard delivered.
India: Concrete is measured in cubic meters. Ready-mix concrete (RMC) costs ₹4,000-7,000 per cubic meter depending on grade (M20, M25). Bagged cement is used for smaller projects — one bag of cement (50 kg) costs ₹350-400.
UK: Concrete is sold by the cubic metre. Ready-mix concrete costs £80-120 per cubic metre delivered. For small projects, ballast and cement are bought separately — 1 ton of ballast costs £40-60 and a 25 kg bag of cement costs £5-8.
Always add 5-10% extra for waste and spillage, and consult local building codes for minimum slab thickness requirements in your area.
Frequently Asked Questions
How much concrete do I need for a concrete slab?
The volume of concrete needed equals length × width × depth. For example, a 10 ft × 10 ft slab at 4 inches deep requires approximately 1.23 cubic yards of concrete. Our calculator handles the conversion from inches to feet and cubic feet to cubic yards automatically.
How many bags of concrete do I need per cubic yard?
A 60 lb bag of concrete mix yields approximately 0.45 cubic feet. Since one cubic yard equals 27 cubic feet, you need about 60 bags of 60 lb mix per cubic yard. An 80 lb bag yields 0.60 cubic feet, so you would need about 45 bags per cubic yard.
What is the standard depth for a concrete slab?
Standard concrete slab depths vary by application: 4 inches for patios, sidewalks, and residential floors; 5-6 inches for driveways; 6-8 inches for garages and light commercial; and 8-12 inches for heavy commercial or industrial applications. Always consult local building codes for minimum requirements.
How much does a cubic yard of concrete weigh?
One cubic yard of concrete weighs approximately 4,000 pounds or about 2 tons. This is based on concrete's typical density of 150 pounds per cubic foot. The total weight of your slab is calculated by multiplying the volume in cubic feet by 150 lbs.
Should I add a waste factor when ordering concrete?
Yes, experienced contractors recommend adding 5-10% extra to account for spillage, uneven subgrades, and slight variations in depth. For small DIY projects, add 10%; for larger commercial pours with experienced crews, 5% is usually sufficient.
Can I pour a concrete slab myself?
Small slabs under 10×10 feet can be a manageable DIY project using bagged concrete mix. For larger slabs, ready-mix concrete delivered by truck is more economical and practical. Ensure you prepare a proper gravel base, install reinforcement (rebar or wire mesh), and allow at least 7 days for curing before heavy use.
How long does concrete take to cure before I can walk or drive on it?
Concrete typically sets within 24-48 hours enough to walk on, but reaches full structural strength after 28 days of curing. For driveways, wait at least 7 days before driving on the slab. Keep the surface moist during the curing process to prevent cracking.
What is the difference between concrete and cement?
Cement is a binding ingredient used in concrete. Concrete is a mixture of cement, water, sand, and gravel (aggregate). Think of cement as the glue that holds the aggregates together. All concrete contains cement, but cement alone is not concrete.