Free Contractor Tool
Concrete Calculator
Enter your slab, footing, column, or circular pour dimensions to instantly get concrete volume in cubic yards and cubic feet, plus 40, 60, and 80 lb bag counts and estimated ready-mix cost. Add multiple pours and a waste factor for a complete order.
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Calculate How Much Concrete You Need
Choose a shape, enter your dimensions, and add as many pours as you need. Pick a waste factor and, optionally, your local ready-mix price. Results update instantly.
Your pour
33.33 cu ft
Extra volume added for spillage, over-excavation, and uneven subgrade.
Enables an estimated ready-mix material cost.
Concrete needed (includes 10% waste)
Cubic yards
1.36
Cubic feet
36.67
80 lb bags
62
Ready-mix cost
Enter price above
Bagged mix estimates
40 lb bags
123
60 lb bags
82
80 lb bags
62
Bag counts are rounded up and already include your selected waste factor. Bagged mix is best for small pours; use ready-mix for a cubic yard or more.
Concrete Reference Guide
Bags per cubic yard, recommended slab thicknesses, and the core formula for estimating concrete on any pour.
Slab thickness guide
Always follow local code and any engineered drawings. Slabs carrying vehicles or heavy loads should be reinforced.
How to calculate concrete
The core formula is simple: get every dimension into feet, multiply length × width × depth to find cubic feet, then divide by 27 to convert to cubic yards, because there are 27 cubic feet in a cubic yard.
Cubic yards = (L ft × W ft × Depth ft) ÷ 27
To convert a thickness in inches to feet, divide by 12. Example: a 4" slab is 4 ÷ 12 = 0.333 ft deep.
For round columns, volume = π × (radius in feet)² × height in feet. This calculator applies the right formula automatically for each shape and then adds your chosen waste factor.
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Common Questions About Calculating Concrete
How do you calculate how much concrete you need?
Measure length, width, and thickness, convert everything to feet, and multiply them to get cubic feet: length (ft) × width (ft) × thickness (ft). Divide thickness in inches by 12 to get feet. Then divide total cubic feet by 27 to get cubic yards, since a cubic yard is 27 cubic feet. This calculator handles slabs, columns, and circular pours automatically.
How many cubic yards of concrete do I need for a slab?
Multiply slab length in feet by width in feet by thickness in feet, then divide by 27. A 10 ft × 10 ft slab at 4 inches thick is 10 × 10 × (4 ÷ 12) = 33.3 cubic feet, or about 1.24 cubic yards. Add 5–10% for spillage and uneven subgrade so you do not run short mid-pour.
How many bags of concrete are in a cubic yard?
One cubic yard is 27 cubic feet, so it takes roughly 45 bags of 80 lb mix, 60 bags of 60 lb mix, or 90 bags of 40 lb mix to fill a cubic yard. Bagged mix works for small pours; for a cubic yard or more, ready-mix delivery is usually cheaper and faster.
How thick should a concrete slab be?
Four inches is typical for patios, walkways, and light foot-traffic slabs. Driveways and garage floors that carry vehicles should be 5 to 6 inches thick. Slabs supporting heavy equipment or commercial loads are usually 6 inches or more with reinforcement. Always follow local code and engineered drawings.
How much does a yard of concrete cost?
In 2026, ready-mix concrete typically runs about $125 to $150 per cubic yard delivered, varying by region, PSI strength, and delivery distance. Small loads and short-load fees can raise the effective price. Enter your local price in the calculator for an estimated material cost.
Should I add extra concrete for waste?
Yes — always order 5 to 10% more than the raw calculated volume for spillage, over-excavation, uneven subgrade, and forms that spread under load. Running short mid-pour means a cold joint or a second delivery. This calculator includes a waste factor selector so your final quantity already has the buffer.
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Book a Free DemoConcrete estimates are based on standard bag yields and geometric volume, plus your selected waste factor. Actual yield varies with mix design, consolidation, and subgrade conditions. Verify quantities against supplier data and engineered drawings before ordering.