How much a boulder weighs by size, how to check the math yourself, and how to set boulders so they look like they belong in a High Desert or Inland Empire yard.
Get a Free Rockscape EstimateLandscape boulders are single large stones, usually 12 inches to 3 feet and up, used to anchor a rock yard, hold a grade change or frame plants. They are heavier than most people expect: a round 2 foot granite boulder weighs about 700 lb and a 3 foot boulder about 2,400 lb, because weight goes up with the cube of the diameter. Anything past roughly a 1 foot cube of solid stone (about 170 lb) needs equipment, not two people.
The weights above come from stone-calculator.org. Below is a full chart, the method behind it so you can check it, and what changes the number for a real boulder.
This page is part of our landscape rock and decomposed granite guide. For a boulder weight calculator, use the landscape rock calculator.
Estimated weight of a round boulder by diameter. Granite uses 168 lb per cubic foot and sandstone 140 lb per cubic foot (stone-calculator.org).
| Diameter | Granite (approx.) | Sandstone (approx.) |
|---|---|---|
| 12 in (1 ft) | 90 lb | 75 lb |
| 18 in (1.5 ft) | 300 lb | 250 lb |
| 24 in (2 ft) | 700 lb | 590 lb |
| 30 in (2.5 ft) | 1,375 lb | 1,145 lb |
| 36 in (3 ft) | 2,375 lb (about 1.2 tons) | 1,980 lb (about 1 ton) |
| 48 in (4 ft) | 5,630 lb (about 2.8 tons) | 4,690 lb (about 2.3 tons) |
| 60 in (5 ft) | 11,000 lb (about 5.5 tons) | 9,160 lb (about 4.6 tons) |
Worked example: a 30 inch granite boulder is 2.5 ft across. 2.5 cubed is 15.6. Times 0.524 is about 8.2 cubic feet. Times 168 is about 1,375 lb.
Our landscape rock calculator includes a boulder weight calculator. Enter the length, width and height and pick a stone type, and it does the math above for you.
To do it by hand for a boulder that is not round, measure length, width and height in feet and average them for a working diameter, then use the sphere formula. For a blocky boulder, multiplying length x width x height gives a box volume, which is the upper limit. The real weight falls somewhere between the sphere and the box. If the number matters, such as for a crane pick or a truck limit, ask the yard for the scale weight.
A useful shortcut when buying: Majestic Rock & Material sells boulders by the ton (Majestic). From the chart, one ton of granite is a round boulder somewhere between 30 and 36 inches across.
Three things move the number: the kind of stone, the shape, and how solid it is.
| Stone | Density (lb per cubic foot) |
|---|---|
| Granite | 168 |
| Slate | 168 |
| Limestone | 160 |
| Sandstone | 140 |
Source: stone-calculator.org. Other sources put granite at about 165 to 175, commonly 170. Southwest Boulder’s chart page also notes that granite and limestone boulders weigh more than sandstone (Southwest Boulder).
Stone-calculator.org puts the practical limit at about a 1 foot cube of solid stone, around 170 lb. Past that, two people cannot comfortably carry it (stone-calculator.org). Most landscape boulders are well past that line.
Most boulders sold in Southern California are granite in gold, tan, brown and gray tones, which match the local soil. A few options from local sources:
Pick boulders at the yard in person if you can. Two boulders of the same listed size can look completely different, and the face you like should be the one that ends up facing the house. For the ground rock around them, see our types of landscape rock guide.
Boulder layout is a big part of our rockscape design work, and it is worth getting right because moving a 1,000 lb stone twice is no fun.
Local examples: Apple Valley rockscape and Hesperia rockscape.
A round granite boulder weighs about 90 lb at 1 foot across, 700 lb at 2 feet and about 2,375 lb at 3 feet. Those are estimates using a sphere and 168 lb per cubic foot for granite. Flat or blocky boulders weigh more.
Measure the diameter in feet, cube it, multiply by 0.524 to get cubic feet for a sphere, then multiply by the stone density (168 lb per cubic foot for granite). Our landscape rock calculator does this for you.
Stone-calculator.org puts the comfortable limit at about a 1 foot cube of solid stone, around 170 lb. Anything bigger should be moved with a dolly rated for the load or with equipment.
Deep enough that it does not look like it was dropped on top and does not rock when you push it. A common practice is to set the widest part near ground level. In the High Desert that often means digging through caliche.
Yes. Granite is about 168 lb per cubic foot and sandstone about 140, so a granite boulder weighs about 20 percent more than a sandstone boulder of the same size.
We checked every number on this page against the public sources below. If a rule or date changes, the agency page is the final word.
Boulders are heavy, hard to move twice, and they change how water and light move through a yard. Monarch places boulders as part of full rockscape installs across the High Desert and Inland Empire. Book a free consultation and we will lay out where they should go.
Get a Free Rockscape EstimateOr call (760) 792-7627
