Driveway estimating
A driveway estimate usually starts as slab math, then gets adjusted for thickness, multiple rectangles, flared aprons, waste, and supplier minimums.
A 12 ft x 30 ft driveway at 5 in thick is 12 x 30 x 0.417 = 150 cubic feet. Divide by 27 and the base volume is 5.56 cubic yards. With 10% waste, the order is about 6.11 cubic yards.
If the driveway has a wider apron, calculate the straight section and the apron separately, then add the yardage.
Many residential driveways use 5 to 6 inches of concrete over a compacted base. Vehicle weight, soil, drainage, reinforcement, climate, and local practice all matter.
Ask your contractor, inspector, or supplier before using a thin slab for vehicle traffic.
Decision guide
Driveway volume depends on formed area and thickness, while performance also depends on base support, drainage, reinforcement, joints, concrete properties, finishing, and curing. Vehicle type and local freeze-thaw exposure can change requirements. Use a qualified local designer or contractor where structural or code questions apply.
The clean volume is 20 x 40 x (5/12) = 333.3 cubic feet, or about 12.35 cubic yards. A 10% planning allowance gives about 13.58 yards, but measured grade variation should be added explicitly before the incidental allowance.
Ready-mix requirements depend on anticipated loads, environmental exposure, and service conditions. NRMCA recommends ordering by measurable performance needs and coordinating placement details. The supplier can help select a mixture, but project design remains the purchaser's responsibility.