Concrete Driveway Calculator
Estimate driveway concrete by length, width and thickness. See cubic yards, 80 lb bag equivalent and a supplier-increment order suggestion.
Quick answer
A 20 × 12 ft driveway at 4 in needs 2.96 yd³ exact. With 10% extra it is 3.26 yd³, or 3.5 yd³ when rounded to a 0.5 yd³ supplier increment.
How this estimate works
Length × width × thickness in feet ÷ 27 gives exact cubic yards. Add your allowance, then round up to the supplier increment you entered. Bags use an example yield of 0.60 ft³ per 80 lb bag.
Before you order
A driveway may include a thickened edge or apron that a simple rectangular estimate omits. Measure those separately in the multi-pour calculator. Thickness, reinforcement and base design depend on your plans and local conditions.
Ask the supplier about minimum loads, order increments and delivery charges. The suggested quantity is a rounding aid, not a supplier quote.
Common driveway dimensions
These examples use a flat rectangular pour at 4 in and an editable 10% allowance. They are quantity examples, not a driveway thickness specification. Measure the actual forms and check the design required for your vehicle loads and soil.
| Finished area | Exact at 4 in | With 10% extra | 80 lb bags |
|---|---|---|---|
| 10 × 20 ft | 2.47 yd³ | 2.72 yd³ | 123 |
| 12 × 20 ft | 2.96 yd³ | 3.26 yd³ | 147 |
| 16 × 24 ft | 4.74 yd³ | 5.21 yd³ | 235 |
| 20 × 20 ft | 4.94 yd³ | 5.43 yd³ | 245 |
| 20 × 24 ft | 5.93 yd³ | 6.52 yd³ | 294 |
A 20 × 12 ft driveway is 240 ft². At 4 in, it needs 80 ft³, or 2.96 yd³ before allowance. Add 10% to reach 3.26 yd³; at a 0.5 yd³ supplier increment, the suggested order is 3.5 yd³.
Edges, apron and slope
A thickened perimeter is extra concrete beyond the uniform slab shown in the table. Measure its added cross-section and length separately so it is not counted twice. An apron or ramp with a different thickness is another distinct pour. Enter those pieces in the multi-pour estimator and keep the driveway name on each line.
Slope changes the amount of excavation and base preparation; it does not by itself change volume when the slab is truly uniform thickness. If thickness varies, measure the actual average or split the area into segments. The gravel base tool and rebar layout tool are separate planning aids, not design approvals.
Questions before you order
Does this include a thickened edge?
No. This calculator treats the driveway as one uniform rectangular slab. Add the extra edge geometry in the multi-pour estimator.
Should I use the suggested order as my supplier quote?
No. It rounds your volume to the increment you enter. The supplier may require a minimum load or charge a small-load fee.
Can I enter a driveway that widens near the street?
Measure the widening as a second non-overlapping rectangle in the multi-pour estimator. Avoid counting the shared area twice.
Continue planning
Content and calculator by pourmeasure. Formula and assumption notes: methodology and sources. Updated October 2026. No independent engineering review is claimed.