Concrete Calculator

Calculate how much concrete you need for slabs, columns, footings, stairs, and curbs. Get cubic yards, bags needed, and cost estimates.

Concrete Needed

Cubic Yards

1.23

Ready-mix order

Cubic Feet

33.3

Cubic Meters0.94
80 lb Bags56
Est. Cost$185

Project Type

Dimensions

Bags Needed (Pre-mixed)

40 lb Bags

112

0.30 cu ft each

60 lb Bags

75

0.45 cu ft each

80 lb Bags

56

0.60 cu ft each

For projects over 1 cubic yard (like yours!), consider ordering ready-mix concrete for better results and cost savings.

Cost Estimate

Ready-Mix (~$150/yd³)$185
Delivery Fee (typical)$75 - $150
80 lb Bags (~$5.50/bag)$308
Recommended OptionReady-Mix

Calculation Formula

Slab Volume:

V = Length × Width × Depth

Conversion:

33.3 cu ft ÷ 27 = 1.23 cubic yards

Pro Tips

  • •Order 5-10% extra concrete to account for waste, spillage, and slight grade variations.
  • •For slabs, a 4-inch minimum thickness is standard; use 6 inches for driveways with heavy vehicles.
  • •Always prepare a proper gravel base (4-6 inches) and compact it before pouring.
  • •Consider adding rebar or wire mesh for driveways, patios, and any load-bearing surfaces.
  • •Weather matters: avoid pouring concrete in extreme heat (>90°F) or if rain is expected within 24 hours.

Quick Answer

To calculate concrete needed: multiply Length x Width x Depth (in feet) to get cubic feet, then divide by 27 to convert to cubic yards. For a 10x10 ft slab that is 4 inches deep: 10 x 10 x 0.33 = 33 cubic feet / 27 = 1.22 cubic yards. Always order 5-10% extra for waste. An 80 lb bag covers 0.6 cubic feet. Ready-mix is more economical for projects over 1 cubic yard.

Key Facts

  • Formula: Cubic Yards = (Length x Width x Depth in feet) / 27
  • One cubic yard = 27 cubic feet of concrete
  • Standard 80 lb bag yields 0.6 cubic feet (need 45 bags per cubic yard)
  • 60 lb bag yields 0.45 cubic feet; 40 lb bag yields 0.3 cubic feet
  • Minimum driveway thickness: 4 inches; 6 inches for heavy vehicles
  • Ready-mix concrete costs $100-150 per cubic yard plus $50-150 delivery
  • Always add 5-10% extra for waste, spillage, and uneven ground
  • Concrete cures in 24-48 hours but reaches full strength in 28 days

Frequently Asked Questions

Calculate volume by multiplying length × width × depth. For a 10×10 ft slab that's 4 inches deep: 10 × 10 × 0.33 = 33 cubic feet = 1.22 cubic yards. Always order 5-10% extra for waste and spillage.
An 80 lb bag yields about 0.6 cubic feet. A 60 lb bag yields about 0.45 cubic feet. A 40 lb bag yields about 0.3 cubic feet. For small projects, bags work well. For anything over 1 cubic yard, consider ready-mix delivery.
Residential driveways should be 4-6 inches thick. Light traffic areas: 4 inches. Heavy vehicles or frequent use: 5-6 inches. Commercial driveways: 6-8 inches. Always use proper base preparation and reinforcement.
Ready-mix concrete costs $100-150 per cubic yard plus delivery ($50-150). Bagged concrete: $4-6 per 80 lb bag. For large projects, ready-mix is more economical. Colored or specialty concrete costs 20-50% more.
Use bagged concrete for small projects under 0.5 cubic yards (like fence posts, small repairs). Use ready-mix for larger projects (driveways, patios, foundations). Ready-mix is more consistent, saves labor, and is cheaper for volume.