How this material calculator works
Estimating bulk materials always comes down to volume. First find the area you are covering by multiplying length by width in feet. Then multiply that area by the depth — converted from inches to feet by dividing by 12 — to get the volume in cubic feet. To convert to cubic yards, the unit landscaping suppliers usually price by, divide the cubic feet by 27, because a cubic yard is 3 ft × 3 ft × 3 ft.
How that volume turns into an order depends on the material. Mulch and topsoil often come in bags of about 2 cubic feet, so dividing the volume by 2 gives the bag count. Gravel is commonly sold by weight, and a cubic yard weighs roughly 1.4 tons. Concrete is sold by the bag, where a 60 lb bag yields about 0.45 cubic feet and an 80 lb bag about 0.60 cubic feet of mixed concrete. In every case, round the number of bags up so you do not come up short.
| Depth | Cu ft per 100 sq ft | Cu yd per 100 sq ft |
|---|---|---|
| 1 inch | 8.33 | 0.31 |
| 2 inches | 16.67 | 0.62 |
| 3 inches | 25.00 | 0.93 |
| 4 inches | 33.33 | 1.23 |
| 6 inches | 50.00 | 1.85 |
Reference note: figures are estimates. Bag yields, gravel density (≈ 1.4 tons per cubic yard) and bag sizes vary by product and moisture, so confirm with your supplier and order a little extra for settling and waste.
Frequently asked questions
- How much mulch do I need?
- Multiply the bed area in square feet by the depth in feet for cubic feet, then divide by 27 for cubic yards. A 100 sq ft bed at 3 inches deep is 25 cubic feet, about 0.93 cubic yards, or 13 bags at 2 cubic feet each.
- How many cubic feet are in a cubic yard?
- There are 27 cubic feet in a cubic yard, because a cubic yard is 3 ft × 3 ft × 3 ft. Divide a cubic-foot total by 27 to convert to cubic yards.
- How many bags of concrete do I need?
- Divide the volume in cubic feet by the bag yield: about 0.45 cu ft for a 60 lb bag and 0.60 cu ft for an 80 lb bag. A 10 cubic foot pour needs about 23 sixty-pound or 17 eighty-pound bags. Round up.
- How much does a cubic yard of gravel weigh?
- Roughly 1.4 tons, about 2,800 pounds, though it varies with stone type and moisture. Multiply your cubic-yard total by 1.4 to estimate the tonnage to order.
- How deep should mulch or gravel be?
- Mulch is usually 2 to 3 inches deep and decorative gravel 2 to 3 inches; gravel for driveways or a base layer is often 3 to 4 inches or more. Deeper layers need proportionally more material.
- How do I calculate soil for a garden bed?
- Multiply length × width × (depth ÷ 12) for cubic feet, then divide by 27 for cubic yards. A 4 ft × 8 ft bed filled 10 inches deep is about 26.7 cubic feet, roughly 0.99 cubic yards.