How to use this gravel and mulch calculator
Pick the material, measure the length and width of the area, and choose the depth you want to spread. The calculator gives the volume in cubic yards (or cubic meters), the approximate weight, which is how many quarries and landscape yards sell stone, and the number of bags if you'd rather buy from a garden center.
For a curved bed, measure its longest length and average width, or split it into a few rectangles. For a circle, multiply the radius by itself and by 3.14 to get the area, then enter that as length with a width of 1.
The formula
Cubic yards = length (ft) × width (ft) × depth (in) ÷ 12 ÷ 27
Dividing by 12 turns inches of depth into feet, and dividing by 27 turns cubic feet into cubic yards. To get tons, multiply cubic yards by the material's weight per yard.
Worked example: a 20 × 10 ft path covered with 3 inches of pea gravel. 20 × 10 = 200 ft². 200 × 3 ÷ 12 = 50 ft³. 50 ÷ 27 = 1.85 cubic yards. Pea gravel weighs about 2,800 lb per cubic yard, so that's about 5,200 lb, or 2.6 tons. In 0.5 ft³ bags, you'd need 100 of them, which is why bulk delivery is usually the better deal for anything over a yard.
How much area does a cubic yard cover?
| Depth | One cubic yard covers |
|---|---|
| 1 in | 324 ft² |
| 2 in | 162 ft² |
| 3 in | 108 ft² |
| 4 in | 81 ft² |
| 6 in | 54 ft² |
Typical weights and depths
| Material | Weight per yd³ | Common depth |
|---|---|---|
| Pea gravel / river rock | ≈ 2,800 lb (1.4 tons) | 2–3 in for paths |
| Crushed stone / road base | ≈ 2,700 lb (1.35 tons) | 4 in+ for bases, in compacted layers |
| Sand | ≈ 2,700 lb (1.35 tons) | 1 in under pavers |
| Topsoil | ≈ 2,100 lb (1.05 tons) | 4–6 in for a new lawn |
| Mulch | ≈ 400–800 lb | 2–4 in in beds |
Weights vary with moisture and stone size, so wet material weighs more. If a supplier sells by the ton, ask what their material weighs per yard.
Tips for ordering
- Compaction shrinks gravel. Crushed stone bases settle by roughly 10–20% when compacted, so order a little extra for driveways and patio bases.
- Lay landscape fabric first under decorative gravel to slow weeds and stop stone sinking into soil.
- Keep mulch away from stems and siding. Leave a few inches of gap around tree trunks and the house to prevent rot and pests.
- Check delivery access. A loaded dump truck is heavy. Ask where it can safely tip without damaging your driveway or lawn.
Frequently asked questions
How many tons of gravel do I need?
Work out the volume in cubic yards (length × width × depth in inches ÷ 324), then multiply by about 1.4 for gravel. A 20 × 10 ft area at 3 inches deep is 1.85 cubic yards, or about 2.6 tons.
How many bags of mulch are in a yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 ft³ mulch or 9 bags of 3 ft³ mulch.
How deep should gravel be for a driveway?
Gravel driveways are usually built in layers: a compacted base of larger crushed stone, then a few inches of smaller surface stone, often 8–12 inches in total. Soft or wet ground may need more, plus a geotextile fabric.
Is it cheaper to buy gravel in bags or in bulk?
Bulk is almost always cheaper per yard once you need more than about half a cubic yard, even with a delivery fee. Bags make sense for small beds, planters and repairs, or where a truck can't reach.
Results are estimates. Material weight varies with moisture and grading; confirm with your supplier before ordering by the ton.