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

volumeCuFt = 120 × (4/12) = 40 cu ftvolumeCuYd = 40 / 27 = 1.48totalCuYd = ⌈1.48 × 1.10 × 10⌉ / 10 = 1.7 cu ydbags80lb = ⌈1.7 × 27 × 1.667⌉ = 77 bags

areaFt² = 60 × (16/12) = 80 sq ftvolumeCuFt = 80 × (8/12) = 53.3 cu ftvolumeCuYd = 53.3 / 27 = 1.97totalCuYd = ⌈1.97 × 1.05 × 10⌉ / 10 = 2.1 cu yd

Common Use Cases

• Driveways and garage slabs
• Patios and sidewalks
• Foundation footings
• Retaining wall footers
• Pool decks and equipment pads
• Curbs and gutters

Notes

• For projects over 1 cu yd, ready-mix delivery is more cost-effective than bag mixing.
• Add 10% waste for uneven ground; 5% for prepared subgrade.
• Common PSI grades: 2,500 PSI (sidewalks), 3,000 PSI (driveways), 4,000 PSI (structural / heavy load), 5,000+ PSI (commercial).
• Cure time: walk on at 24 hours, drive on at 7 days, full strength at 28 days.
• One 80lb bag = 0.6 cu ft mixed; one 60lb bag = 0.45 cu ft mixed.

Frequently Asked Questions