Calculating Concrete for a Driveway
A concrete driveway is just a thick slab — the calculation is straightforward. The key decisions are thickness (4 inches for passenger cars, 6 inches for trucks) and whether you need base preparation (almost always yes). Enter your driveway length and width as the slab dimensions, set thickness to 4 or 6 inches, and the calculator returns cubic yards for your ready-mix order.
Most residential driveways are well beyond the bag threshold. A single-car driveway at 10 ft × 40 ft is 4.9 cubic yards — about 220 bags of 80 lb mix. Call a ready-mix supplier.
Driveway Thickness: 4 or 6 Inches?
- 4 inches — standard residential passenger vehicle driveway. Adequate for cars, sedans, and SUVs. Should be reinforced with 6×6 wire mesh or #3 rebar at 18-inch centres. The minimum most contractors will pour for a residential driveway.
- 6 inches — heavy use or heavy vehicles. Required if pickup trucks, delivery vans, RVs, or boats will park regularly. Six-inch concrete with #4 rebar is significantly more resistant to cracking under point loads.
- Base preparation — Regardless of thickness, a 4–6 inch compacted aggregate base (gravel) under the slab is standard practice. It provides drainage, prevents frost heaving, and gives a stable substrate. Budget the base gravel separately using the Gravel Calculator.
- Expansion joints — Control joints every 8–10 feet prevent random cracking by creating deliberate weak points. They should be cut to one-quarter of the slab depth (1 inch for a 4-inch slab) within 12 hours of the pour.
- Cure time — Keep the driveway moist for 7 days. No vehicle traffic for 7 days minimum; full strength at 28 days. Avoid de-icing salts for the first winter — they accelerate surface spalling in new concrete.
Driveway concrete typically specs 4,000 PSI with air entrainment in freeze-thaw climates. Tell your ready-mix supplier what you're pouring — they'll set the mix design accordingly.
Need a different shape? The full Concrete Calculator covers slabs, footings, round columns, and post holes in one place.