Concrete Calculator for Slabs, Bags, Yards & Cost

Calculating yards of concrete involves finding the volume in cubic feet first, then dividing by 27 (since 1 cubic yard = 27 cubic feet). The formula is: (Length in feet × Width in feet × Thickness in feet) ÷ 27 = Cubic Yards. For a typical 4-inch thick driveway that's 20ft × 30ft: (20 × 30 × 0.33) ÷ 27 = 7.33 cubic yards. Always add 10% for waste, making it 8.06 yards. Our concrete calculator yards feature does this math instantly and includes waste calculations.

Our concrete bag calculator instantly converts cubic yards to bags. One cubic yard typically requires: 45 bags of 80lb concrete, 60 bags of 60lb concrete, or 90 bags of 40lb concrete. For example, a 2 cubic yard project needs 90 bags of 80lb concrete. The calculator shows all three bag sizes simultaneously, helping you choose based on price and handling preference. It also factors in your selected waste percentage for accurate purchasing.

To calculate concrete for a slab, measure length and width in feet, and thickness in inches. Convert thickness to feet (divide by 12), then multiply all three dimensions. A 12ft × 16ft patio with 4-inch thickness needs: 12 × 16 × 0.33 = 63.36 cubic feet or 2.35 cubic yards. Our concrete slab calculator simplifies this process - just enter dimensions in any unit and instantly see yards, bags needed, weight, and estimated cost with customizable pricing.

Our concrete calculator handles multiple shapes beyond basic slabs. For cylinders/columns: π × radius² × height. For footings: length × width × depth. For steps: (rise × run × width × number of steps). For curbs: complex cross-sectional area × length. Each shape has its own dedicated calculator with visual preview, ensuring accurate calculations for any project type. Simply select your shape, input dimensions, and get precise concrete requirements instantly.

Converting concrete yards to bags depends on bag size. Standard conversions: 1 cubic yard = 45 bags (80lb), 60 bags (60lb), or 90 bags (40lb). For partial yards, multiply accordingly. Example: 0.5 yards needs 23 bags of 80lb concrete. Our calculator automatically shows all three bag sizes with exact counts, including fractional bags. This helps you decide between buying fewer heavy bags or more lighter bags based on your handling capabilities.

Concrete typically weighs 150 pounds per cubic foot or 4,050 pounds per cubic yard. To calculate cost, multiply cubic yards by price per yard (usually £120-£160). Our concrete cost calculator shows both weight (important for delivery planning) and cost estimation with customizable pricing. You can adjust the price per yard based on local rates and instantly see total project cost, helping with accurate budgeting and contractor comparisons.

Our concrete calculator stands out with unique features: calculates 5 different shapes (slab, cylinder, steps, footing, curb), shows instant bag requirements for all sizes, generates professional PDF reports for permits and contractors, includes customizable waste factor (5-15%), supports both imperial and metric units, and provides real-time cost estimation. Unlike basic calculators, we offer a complete solution from planning to purchasing, making it the most comprehensive concrete calculator available online.