The coverage formula
Coverage is the rock calculator run backwards. Turn the amount into cubic feet, then divide by the depth in feet:
square feet = cubic feet ÷ (depth in inches ÷ 12)
cubic feet = cubic yards × 27 or tons × 2,000 ÷ lb per cu yd × 27
For a ton of rock at about 2,700 lb per cubic yard: 2,000 ÷ 2,700 = 0.74 cu yd = 20 cu ft. At 3 inches (0.25 ft) that covers 20 ÷ 0.25 = 80 sq ft.
Coverage of one cubic yard
A cubic yard is 27 cubic feet of anything, so this table works for every rock type:
| Depth | 1 cu yd covers | 1/2 cu yd covers |
|---|---|---|
| 1 inch | 324 sq ft | 162 sq ft |
| 2 inches | 162 sq ft | 81 sq ft |
| 2.5 inches | 130 sq ft | 65 sq ft |
| 3 inches | 108 sq ft | 54 sq ft |
| 4 inches | 81 sq ft | 40.5 sq ft |
| 6 inches | 54 sq ft | 27 sq ft |
Coverage of one ton, by rock type
A ton is a weight, so how far it goes depends on how heavy the rock is:
| Rock (about lb per cu yd) | 1 ton = cu ft | at 2” | at 3” | at 4” |
|---|---|---|---|---|
| River rock, landscape rock, crushed granite, marble chips (2,700) | 20 | 120 sq ft | 80 sq ft | 60 sq ft |
| Mexican beach pebbles (2,800) | 19.3 | 116 sq ft | 77 sq ft | 58 sq ft |
| Decomposed granite, loose (2,600) | 20.8 | 125 sq ft | 83 sq ft | 62 sq ft |
| Cobblestone (2,600) | 20.8 | n/a | n/a | 62 sq ft |
| Lava rock (1,200) | 45 | 270 sq ft | 180 sq ft | 135 sq ft |
Decomposed granite that is compacted covers less than the table shows; see the decomposed granite calculator for the allowance.
Coverage of bags
| Depth | 0.5 cu ft bag | 1 cu ft bag | Bags of 0.5 cu ft per 100 sq ft |
|---|---|---|---|
| 2 inches | 3 sq ft | 6 sq ft | 34 |
| 3 inches | 2 sq ft | 4 sq ft | 50 |
| 4 inches | 1.5 sq ft | 3 sq ft | 67 |
Worked examples
Three tons of river rock at 3 inches. 3 × 20 cu ft = 60 cu ft. 60 ÷ 0.25 = 240 sq ft, for example a 24 × 10 ft bed.
Half a yard at 2 inches. 0.5 × 27 = 13.5 cu ft. 13.5 ÷ (2 ÷ 12) = 81 sq ft.
Ten bags at 2 inches. 10 × 0.5 = 5 cu ft. 5 ÷ 0.1667 = 30 sq ft, about a 5 × 6 ft patch.
One ton of lava rock at 2.5 inches. 2,000 ÷ 1,200 × 27 = 45 cu ft. 45 ÷ 0.2083 = 216 sq ft.
What depth should you plan for?
Coverage gets bigger the thinner you spread, but rock that is too thin shows the ground underneath. The site’s rule is about twice the average stone size, at least 2 inches: 2 inches for 3/4 inch rock, 2.5 inches for 1–1½ inch rock, about 4 inches for 1–3 inch river rock. The full table is on the rock calculator.
Why the real coverage can differ
- Uneven ground. Low spots swallow rock. If the bed has dips, plan on the deep end.
- Settling. Rock settles into soil and fabric in the first months. A 10% allowance usually covers it.
- Wet weight. If you bought by the ton and the rock was wet, you received a little less rock than the dry figure suggests.
- Different density. Your supplier’s stone may weigh more or less per yard than our averages. The rock weight calculator shows typical ranges.
These figures assume a flat, evenly raked layer. For a project you have not bought yet, start from your measurements in the rock calculator instead.
Questions people ask
- How many square feet does a ton of rock cover?
- For most landscape rock (about 2,700 pounds per cubic yard), one ton covers about 120 square feet at 2 inches deep, 80 at 3 inches, 60 at 4 inches and 40 at 6 inches. Lava rock covers roughly twice as much per ton.
- How much area does a cubic yard of rock cover?
- 324 square feet at 1 inch deep, 162 at 2 inches, 108 at 3 inches, 81 at 4 inches and 54 at 6 inches. That holds for any rock, because a cubic yard is always 27 cubic feet.
- How do you calculate rock coverage?
- Convert the amount to cubic feet (cubic yards × 27, or tons × 2,000 ÷ pounds per cubic yard × 27), then divide by the depth in feet. For example, 20 cubic feet ÷ 0.25 feet (3 inches) = 80 square feet.
- How much does a bag of rock cover?
- A 0.5 cubic foot bag covers about 3 square feet at 2 inches deep, 2 square feet at 3 inches and 1.5 square feet at 4 inches.