Bags of concrete by bag size
Order options for your project volume including waste.
Home / US Calculators / Concrete Yardage
Home & Yard
Concrete, Mulch & Gravel Yardage Calculator
Enter the length, width and depth of your slab or bed to get cubic feet, cubic yards, and how many bags of concrete or tons of gravel to order, with a waste allowance built in.
Volume to order
1.35 yd³
Cubic feet—
With waste allowance—
80 lb concrete bags—
Concrete needed—
Cubic yards, defined
A cubic yard is a cube 3 feet on each side, 27 cubic feet, and it's how bulk concrete, gravel and mulch are sold. To order the right amount you convert your slab or bed dimensions to feet, multiply to get volume, then divide by 27. Bagged concrete and gravel tonnage are derived from that same cubic-foot figure.
The formula
cubic feet = length(ft) × width(ft) × (depth in ÷ 12)
cubic yards = cubic feet ÷ 27
80 lb bags ≈ cubic feet ÷ 0.60 · gravel tons ≈ yd³ × 1.4
cubic yards = cubic feet ÷ 27
80 lb bags ≈ cubic feet ÷ 0.60 · gravel tons ≈ yd³ × 1.4
Worked example
A 10 × 10 ft slab at 4 inches deep: cubic feet = 10 × 10 × (4 ÷ 12) = 33.3, cubic yards = 33.3 ÷ 27 = 1.23 yd³. Add 10% waste → 1.35 yd³. That's about 33.3 ÷ 0.6 ≈ 56 eighty-pound bags before waste.
Frequently asked questions
How do I calculate cubic yards?
Length × width × depth in feet ÷ 27.
How many bags of concrete are in a yard?
About 45 sixty-pound or 60 eighty-pound bags per cubic yard.
How much does a yard of gravel weigh?
Roughly 1.4 tons (about 2,800 lb).
Should I add extra for waste?
Yes, 5-10% for spillage and uneven subgrade.
How deep should mulch or gravel be?
Mulch 2-3 inches; gravel driveways 4-6 inches.