How thick should a concrete driveway be?

A 4-inch slab is a common residential minimum for passenger vehicles on a sound base. Many contractors use 5 inches for added durability and 6 inches or more for RVs, trucks, weak soils, or concentrated loads. Local design requirements control.

How much waste should I add for a driveway?

Ten percent is a practical planning allowance for most formed driveway pours. Complex aprons, uneven excavation, or irregular edges may justify 12–15%.

How much concrete is needed for a 20 by 20 driveway?

At 5 inches thick, a 20 × 20 ft driveway contains 166.7 ft³, or 6.17 yd³ net. With 10% waste, the order quantity is about 6.79 yd³.

Driveway Concrete Calculator

Calculate concrete for a driveway from its length, width, and slab thickness. Get cubic yards with waste, ready-mix cost, concrete weight, and equivalent 60-pound and 80-pound bag counts.

Driveway Dimensions

Results update as you change the formed dimensions.

Length

Width

Slab thickness

Waste allowance

Ready-mix price

$/yd³

Order quantity

6.79yd³ with waste

Slab area

400ft²

Net volume

166.7ft³

Concrete weight

27,500lb · 13.8 tons

60 lb bags

408bags

80 lb bags

306bags

Estimated ready-mix material cost

$1,086

Includes $0 short-load fee when the order is under 3 yd³. Labor, base, forms, reinforcement, finishing, tax, and other delivery charges are excluded.

Driveway Concrete Thickness and Volume

Four inches is a common minimum for passenger-car driveways on a well-compacted base. Use 5–6 inches for heavier vehicles, poor soils, or frequent truck and RV traffic; engineered conditions may require more.

Driveways carry repeated wheel loads, so base preparation, drainage, joints, reinforcement, and concrete strength matter as much as volume.

How to Calculate Concrete for a Driveway

Multiply the formed length by width and slab thickness after converting thickness from inches to feet. Divide cubic feet by 27 for cubic yards, then add the selected waste allowance.

Rectangular slab order

yd³ = length (ft) × width (ft) × [thickness (in) ÷ 12] ÷ 27 × (1 + waste%)

Measure the inside of the forms. Calculate thickened edges, footings, ramps, and separate pads independently.

Driveway Planning Checklist

Confirm finished width, apron dimensions, and any flared or curved areas.
Use a compacted granular base and slope the slab away from structures.
Plan control joints at appropriate spacing and isolate the slab from foundations.
Verify thickness, reinforcement, and concrete strength for the expected vehicles.