Volume Formula: We calculate cubic feet using Length (ft) x Width (ft) x Thickness (inches / 12). For example, a 10x10 slab at 4 inches thick: 10 x 10 x (4/12) = 33.33 cubic feet. We then convert to cubic yards by dividing by 27, since one cubic yard equals 27 cubic feet. This gives 33.33 / 27 = 1.23 cubic yards.
Bag Estimates: A standard 60lb bag of concrete yields approximately 0.45 cubic feet when mixed. An 80lb bag yields approximately 0.6 cubic feet. We divide the total cubic feet by these yield values and round up to the nearest whole bag, since you cannot purchase partial bags.
10% Waste Factor: Industry standard practice adds 10% to all concrete orders. Concrete is lost to spillage, overfilling forms, subgrade irregularities, and finishing waste. Running short on a pour is far more costly than ordering slightly extra, as partial pours create cold joints that weaken the structure.
Multi-Area Totals: When calculating multiple areas, we sum all individual cubic foot volumes before converting to cubic yards and applying the waste factor. This gives you a single combined order quantity for ready-mix delivery.
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Get Concrete Quotes →A standard concrete mixer truck holds 8-10 cubic yards. Most companies require a minimum order of 1 yard and charge short-load fees for orders under 5 yards.
Most ready-mix companies have a 1-yard minimum with a short-load fee ($50-$100) for orders under 4-5 yards. For very small projects, bags may be more cost-effective.
Residential driveways should be at least 4 inches thick. For heavy vehicles or RVs, 5-6 inches is recommended. Commercial driveways need 6-8 inches minimum.
Bags are practical for projects under 1 cubic yard (about 45 80lb bags). For larger projects, ready-mix delivery is more cost-effective and ensures consistent quality.
Concrete inevitably spills, overfills forms, or gets lost in subgrade irregularities. A 10% waste factor prevents costly short orders and emergency runs.