Concrete Calculator

Formula

volumeCuFt = area × (thickness / 12)volumeCuYd = volumeCuFt / 27totalCuYd = ⌈volumeCuYd × (1 + waste/100) × 10⌉ / 10bags80lb = ⌈totalCuYd × 27 × 1.667⌉

Parameters

Thickness

Slab thickness in inches. 4" for patios, 6" for driveways.

Waste %

Extra for uneven subgrade and spillage. 5–10%.

Results

Cubic Yards

Ready-mix concrete to order.

80lb Bags

Bags for hand-mixing (each = 0.6 cu ft).

Example

volumeCuFt = 500 × (6/12) = 250 cu ftvolumeCuYd = 250 / 27 = 9.26totalCuYd = ⌈9.26 × 1.05 × 10⌉ / 10 = 9.8 cu ydbags80lb = ⌈9.8 × 27 × 1.667⌉ = 441 bags

Common Use Cases

• Driveways and garage slabs
• Patios and sidewalks
• Foundation footings
• Retaining wall footers

Notes

• For projects over 1 cu yd, ready-mix delivery is more cost-effective.
• Add 10% waste for uneven ground.