Key takeaways
- Cubic yards = square feet × depth in inches ÷ 324.
- Weight is only a range, because we found no government density table.
- Keep mulch 2 to 4 inches deep and away from tree trunks.
Enter the area, depth and material. Bulk suppliers usually sell by the cubic yard or ton, and stores by the bag, so the tool gives you both.
How the calculator works
- Cubic yards: square feet × depth in inches ÷ 324, the formula used in a Texas AgriLife fact sheet
- Bags: cubic yards × 27 ÷ bag size in cubic feet, rounded up
- Weight: cubic yards × a density range
Worked example
100 square feet of gravel, 3 inches deep, with 2-cubic-foot bags:
- 100 × 3 ÷ 324 = 0.93 cubic yards
- 25 cubic feet ÷ 2 = 13 bags
- About 1.3 to 1.6 tons, using the commercial range below
How depth changes the amount
For 500 square feet:
| Depth | Cubic yards | 2 cu ft bags |
|---|---|---|
| 2 in | 3.09 | 42 |
| 3 in | 4.63 | 63 |
| 4 in | 6.17 | 84 |
| 6 in | 9.26 | 125 |
Past about a couple of cubic yards, bulk delivery is worth pricing against bags. Ask how close the truck can get.
Why weight is a range
We didn't find a government density table, and commercial figures vary with moisture and product:
| Material | Range used here |
|---|---|
| Gravel | 1.4 to 1.7 tons per cubic yard |
| Mulch | 0.2 to 0.4 tons per cubic yard |
| Topsoil | About 1 to 1.35 tons per cubic yard |
Use these for planning, then ask your supplier for theirs. Check your vehicle's payload rating before hauling, because gravel adds up quickly.
Compaction
Loose gravel and soil settle when compacted, so you may need more than the math says. Some commercial sites quote about 30%, but we couldn't trace that to its source. If you're compacting, ask your supplier and use the extra allowance field.
How deep should mulch be?
University of Vermont Extension says:
- Apply no more than 2 to 4 inches.
- Keep mulch at least 3 inches from the root flare, and don't let it touch the trunk.
- Avoid "mulch volcanoes". Piled mulch can trap moisture against bark, and deep mulch can encourage roots that girdle the tree.
Before you dig
If you're removing soil or digging an edge or base, contact 811 a few business days ahead. Check that the finished grade won't send water toward your foundation or a neighbor's property.
Frequently asked questions
How much does a cubic yard of gravel cover?
At 3 inches deep, about 108 square feet. At 2 inches, about 162.
How many bags of mulch are in a yard?
27 cubic feet is 13.5 bags of 2 cubic feet each, so buy 14.
How do I handle an odd-shaped bed?
Split it into rectangles and enter the total as length × width, or use a length of the total area and a width of 1.
Sources
We use primary sources where we can: building codes, federal rules and manufacturer documents. Read our editorial standards.
- Texas AgriLife fact sheet, hosted by UC ANR: Mulch volume
- University of Vermont Extension: Beware the mulch volcano
- 811: What is 811?