How to Calculate Mulch, Gravel & Aggregate Quantities
To find Cubic Yards: multiply Square Footage × Depth in Inches ÷ 324. One cubic yard of wood mulch requires 13.5 bags (2 cu ft) or 9 bags (3 cu ft). For crushed stone gravel, multiply cubic yards by 1.35 to convert to tons (1 yd³ ≈ 2,700 lbs = 1.35 short tons).
Whether refreshing mulch beds in spring or grading a gravel driveway, ordering the correct quantity requires bridging the gap between 2D area (square feet), depth (inches), and bulk delivery units (cubic yards or short tons).
The “Divide by 324” Shortcut Rule
Because 1 cubic yard equals 27 cubic feet, and 1 foot equals 12 inches: $27 \times 12 = 324$. This yields a universal shortcut formula for any rectangular area:
Example: A 500 sq ft garden bed mulched 3 inches deep:
(500 × 3) ÷ 324 = 1,500 ÷ 324 = 4.63 cu yd (or approx 63 bags of 2 cu ft).
Cubic Yards to Tonnage Conversion
Aggregate suppliers price heavy materials (gravel, stone, sand, asphalt) by the ton rather than the cubic yard.
Example: 10 cubic yards of #57 crushed stone:
10 cu yd × 1.35 tons/yd³ = 13.5 Tons (approx 27,000 lbs).
Annual freshening over existing decomposed mulch beds.
New garden beds to suppress weed growth and retain ground moisture.
Compacted crushed stone base beneath concrete pads or gravel drives.
Structural road base, retaining wall drainage, and foundation backfill.
Frequently Asked Questions
How many bags of mulch are in a cubic yard?
One cubic yard equals 27 cubic feet. A standard 2.0 cu ft bag yields 13.5 bags per cubic yard (27 / 2 = 13.5). A large 3.0 cu ft bag yields exactly 9 bags per cubic yard (27 / 3 = 9).
How many tons is 1 cubic yard of gravel?
One cubic yard of crushed stone gravel (#57) weighs approximately 2,700 pounds, which equals 1.35 US short tons (or about 1.4 tons for wet or denser stone). To convert cubic yards of gravel to tons: multiply yards by 1.35.
How deep should mulch and gravel be applied?
Wood mulch should be applied 2 to 3 inches deep around flowerbeds and trees (avoid piling directly against tree trunks). Gravel driveways should have a 4 to 6-inch compacted base of #57 stone topped with 2 to 3 inches of smaller finishing gravel.
How much material fits in a standard dump truck?
A standard tandem-axle dump truck can carry up to 10 to 12 cubic yards of light material like mulch, or up to 14 to 16 tons of heavy aggregate like gravel and sand before hitting legal highway weight limits.