This concrete driveway calculator estimates how much concrete you need from the driveway’s length, width, and thickness. Enter your dimensions above to get the volume in cubic yards, the number of pre-mixed bags, and a quick material estimate.
How to use this calculator
- Enter the driveway length and width in feet.
- Set the thickness in inches (4″ is standard for cars).
- Read the required cubic yards and bag count in the results.
How is concrete volume calculated?
Concrete is ordered by volume. Convert thickness to feet, multiply the three dimensions, then convert to cubic yards:
Volume (ft³) = Length × Width × (Thickness ÷ 12) Cubic yards = Volume (ft³) ÷ 27
- Length, Width — driveway footprint (feet)
- Thickness — slab depth (inches), divided by 12 to get feet
- 27 — cubic feet in one cubic yard
Example calculation
For a 20 ft × 12 ft driveway poured 4 inches thick:
- Volume = 20 × 12 × (4 ÷ 12) = 80 ft³
- Cubic yards = 80 ÷ 27 = 2.96 yd³
- Add 10% waste → order about 3.3 cubic yards
Always round up and add 5–10% for spillage, uneven subgrade, and over-excavation.
Tips for ordering concrete
- Ready-mix truck is cheaper per yard for jobs above ~1 cubic yard.
- Bags suit small repairs: an 80-lb bag yields ~0.6 ft³, so ~45 bags per cubic yard.
- Compact the base and use rebar or mesh to limit cracking.
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Frequently Asked Questions
How much concrete do I need for a driveway?
Multiply length by width by thickness in feet, then divide by 27 to get cubic yards. A 20 x 12 ft driveway at 4 inches thick needs about 3 cubic yards.
How thick should a concrete driveway be?
Four inches is standard for cars; use five to six inches if trucks or heavy vehicles will park on it. Thicker slabs resist cracking under load.
How many 80-lb bags of concrete are in a cubic yard?
About 45 bags of 80-lb pre-mixed concrete make one cubic yard, since each bag yields roughly 0.6 cubic feet.