When it comes to landscaping projects using rock, an important consideration is figuring out how much area a certain amount of rock will cover. Rock is often measured by the ton, so a common question that comes up is “how much does 1 ton of rock cover?” The answer depends on several factors, including the size and type of rock and the depth it is laid.
Factors That Determine Rock Coverage
There are a few key factors that determine how much area 1 ton of rock will cover:
- Size of rock – Rock comes in different sizes like pebbles, gravel, cobblestones, etc. Smaller rock takes more rock by weight to cover the same area. Larger, heavier rock covers more area per ton.
- Type of rock – The density and shape of different rock types affects coverage. Irregular, porous rocks may cover less area than smoother, denser rocks.
- Depth of rock – The depth that rock is laid to also affects total coverage. Laying 1 ton of rock 1 inch deep covers more area than laying it 4 inches deep.
So when estimating how far 1 ton of rock will go, you need to account for all these variables. The coverage will be different for 1 ton of pea gravel laid 1 inch deep versus 1 ton of large boulders laid 6 inches deep.
Typical Coverage of 1 Ton of Rock
As a general guideline for medium sized gravel or crushed rock laid 4 inches deep, coverage is:
- 1 ton covers 50-60 square feet
- Therefore, 1 yard (3 tons) covers 150-180 square feet
So if you purchase 1 yard (3 tons) of gravel or crushed rock, you can expect it to cover about a 15 ft x 15 ft area if spread at 4 inch depth. This is just an average – the actual coverage may differ depending on the specific rock size, shape, density, and depth it is laid.
Coverage Chart by Rock Size and Depth
Here is a more detailed chart showing approximate coverage for different rock sizes and depths:
| Rock Type | 1 Inch Depth | 2 Inch Depth | 3 Inch Depth | 4 Inch Depth |
|---|---|---|---|---|
| Pea Gravel | 100 sq ft | 50 sq ft | 35 sq ft | 25 sq ft |
| 1/4″ Crushed Rock | 80 sq ft | 40 sq ft | 30 sq ft | 20 sq ft |
| 3/8″ Crushed Rock | 70 sq ft | 35 sq ft | 25 sq ft | 18 sq ft |
| 3/4″ Crushed Rock | 60 sq ft | 30 sq ft | 20 sq ft | 15 sq ft |
| 1″ Crushed Rock | 50 sq ft | 25 sq ft | 17 sq ft | 13 sq ft |
| 1 1/2″ Crushed Rock | 45 sq ft | 23 sq ft | 15 sq ft | 11 sq ft |
| 2″ Crushed Rock | 40 sq ft | 20 sq ft | 13 sq ft | 10 sq ft |
| 3″ Crushed Rock | 35 sq ft | 18 sq ft | 12 sq ft | 9 sq ft |
So you can see how rock size and depth significantly affect coverage per ton. As a rule of thumb, smaller rock laid shallower covers the most area. Larger rock and deeper depths require more rock by weight but provide a thicker, more durable coverage.
Calculating Exact Coverage
To calculate exactly how much area 1 ton of rock will cover for your specific project, you need to know:
- Dimensions of the area to be covered (length x width)
- Desired depth of the rock in inches
- Weight of rock needed:
- Gravel = 2,700 lbs per cubic yard
- Crushed rock = 2,800 lbs per cubic yard
- Bulk density of the type of rock used
With this information, you can calculate:
- Cubic yards of rock needed = (Area x depth) / 324
- Tons of rock needed = Cubic yards x rock density (in lbs per cubic yard) / 2000 lbs
- Square feet covered by 1 ton = Area (sq ft) / Tons needed
Let’s take an example:
- Area to cover: 20 ft x 10 ft = 200 sq ft
- Desired depth: 4 inches = 0.33 ft
- Rock type: Crushed rock, density 2,800 lbs/cu yd
Calculations:
- Cubic yards needed = (200 sq ft x 0.33 ft depth) / 324 = 0.2 cu yd
- Tons needed = 0.2 cu yd x 2,800 lbs/cu yd / 2000 lbs/ton = 0.28 tons
- Sq ft covered by 1 ton = 200 sq ft / 0.28 tons = ~714 sq ft
So for this specific project, 1 ton of crushed rock would cover about 714 square feet when spread at a depth of 4 inches. This is significantly more than the 50-60 sq ft per ton general guideline. It illustrates why calculating coverage precisely for your specific parameters is important.
Factors that Decrease Coverage
When estimating how far your rock supply will go, keep in mind any factors that may decrease the coverage:
- Waste/Loss – Rock scattering, spillage, and waste will decrease actual coverage.
- Compaction – Compacting rock down will reduce depth and coverage area.
- Irregular contours – Covering surfaces other than flat ground often takes more rock.
- Overlapping – Overlapping rock layers between passes decreases efficiency.
- Landscaping features – Areas taken up by trees, shrubs, pavers, etc. reduces rock cover area.
It’s a good idea to add an extra 10-20% to your rock quantity estimate to account for typical waste and other decreasing factors.
Conclusion
How much area 1 ton of rock covers depends on the specific size and type of rock and the depth it is laid. As a guideline, 1 ton of medium gravel or crushed rock covers 50-60 sq ft at a 4 inch depth. Smaller rock sizes and shallower depths increase coverage, while larger rocks and deeper layers decrease coverage per ton.
To get an accurate estimate for your specific project, calculate the cubic yards of rock needed based on area and depth. Then use the density to find the tons required and divide by the project area. Adding extra rock to account for typical waste and decreasing factors will help ensure you purchase the right amount.
