Guide · Landscaping
How Much Decorative Rock Do I Need per 100 Sq Ft?
The standard rule of thumb: one ton of decorative rock covers about 100 square feet at 2 inches deep. For 3 inches — the depth that actually suppresses weeds — plan on 1.3 tons per 100 square feet.
The exact formula, a coverage table by area and depth, how rock type changes the weight, and fabric and edging guidance — all below. For instant quantities, our free landscape rock calculator converts any area and depth to tons, yards, and bags.
Tons, yards, and bags for your exact area — free, no sign-up.
Open the rock calculator →At 2″ deep. At 3″ deep: ~1.3 tons. Density varies by rock type — confirm with your supplier.
The math, step by step
At 2″: 100 × 2 × 1.4 ÷ 324 = 0.86 → order 1 ton
At 3″: 100 × 3 × 1.4 ÷ 324 = 1.30 → order 1.5 tons
- Start from the rule of thumb. One ton of decorative rock covers about 100 square feet at 2 inches deep — the figure most landscape yards quote.
- Adjust for depth. Weed suppression really wants 3 inches: multiply by 1.5 → about 1.3 tons per 100 ft².
- Do the exact math. Tons = area × depth(in) × 1.4 ÷ 324. For 100 ft² at 2″: 0.86 tons → order 1 ton. At 3″: 1.30 tons → order 1.5 tons.
- Round up to how it’s sold. Landscape yards sell by the ton or half-ton; round up, because a thin spot in rock coverage looks worse than a small surplus (surplus top-ups settle areas and edges).
Decorative rock by area and depth
Tons use a 1.4 tons-per-yard planning density. Confirm your supplier’s coverage — light lava rock and heavy river rock differ.
| Area | At 2″ deep | At 3″ deep |
|---|---|---|
| 50 ft² | 0.43 t (order 0.5) | 0.65 t (order 1) |
| 100 ft² | 0.86 t (order 1) | 1.3 t (order 1.5) |
| 150 ft² | 1.3 t (order 1.5) | 1.94 t (order 2) |
| 200 ft² | 1.73 t (order 2) | 2.59 t (order 3) |
| 300 ft² | 2.59 t (order 3) | 3.89 t (order 4) |
| 500 ft² | 4.32 t (order 4.5) | 6.48 t (order 6.5) |
Order quantities round up to the nearest half ton, the way most yards sell it.
How deep should landscape rock be?
Two inches is the minimum for a finished look; three inches is the working depth for weed suppression and a premium appearance. Match depth to stone size: rock up to 1 inch sits well at 2–3 inches deep, while large 2–3-inch river rock needs 3–4 inches or it looks sparse and wobbles underfoot. Deeper than 4 inches is usually wasted money unless you’re filling a low spot — use compacted soil or road base underneath and rock only on top.
Rock types and what they weigh
The 1.4 tons-per-yard figure fits most common decorative rock — river rock, pea gravel, and crushed granite all land near it. Two exceptions: decomposed granite packs lighter (roughly 1.1–1.3 tons per yard) and is often sold by the yard rather than the ton, and lava rock is dramatically lighter (under a ton per yard) because it’s full of air pockets — it also breaks down faster under foot traffic. When a yard quotes coverage “per ton,” that figure already accounts for their material’s density; when they quote per yard, convert with 1.4 as your planning number and confirm.
Fabric, edging, and the finished job
Rock over bare soil becomes a weed farm within a season. Lay woven landscape fabric first — it suppresses weeds while letting water through. Skip solid plastic sheeting: it traps water, suffocates soil, and turns the bed into a slip-and-slide. Hold the rock in with metal or stone edging at lawn boundaries; without it, mowers fling rock into the grass and the bed edge creeps outward every year. After spreading, a rinse with the hose washes off quarry dust and shows the rock’s true color — do this before judging whether you like the shade you bought.
How rock is sold: ton, yard, or bag
Landscape material yards sell decorative rock by the ton or the yard (about 1.4 tons per yard for most rock), dumped from a truck or loaded into your trailer. Home centers sell 0.5-cubic-foot bags — at 54 bags per yard, bagged rock only makes sense for tiny areas: a 100 ft² bed at 3 inches would need about 35 bags. For anything over a few bags, the yard is cheaper by a wide margin. Delivery fees usually have a minimum, so combine rock with soil or mulch orders when you can. Run your exact area through our landscape rock calculator for tons, yards, and bag counts.
Rock vs. mulch: the long-term math
Rock costs more up front — often several times the price of mulch per square foot installed — but the comparison flips over time. Mulch decomposes and needs topping up every 1–2 years, forever; rock, once installed over fabric with edging, can last 10+ years with only occasional weed-pulling and top-ups where it settles. In hot, dry climates (xeriscaping country), rock also cuts irrigation needs around drought-tolerant plantings. The trade-offs: rock doesn’t feed the soil, it radiates heat that stresses some plants, and fallen leaves are miserable to clean out of it — a leaf blower becomes mandatory equipment. Choose rock for permanent, low-water landscapes and high-visibility beds; choose mulch where soil health and plant vigor matter most.
How we calculate
Tonnage is area (ft²) × depth (inches) × 1.4 ÷ 324, using a 1.4 tons-per-yard planning density for typical decorative rock. Lightweight materials (lava rock, some decomposed granites) differ significantly — use your supplier’s stated coverage when ordering. Order quantities round up to the nearest half ton, the common retail increment. Depth guidance (2–3 inches) is standard landscaping practice; stone size, drainage needs, and HOA rules can change it.
Reviewed September 2026 · TrueMeasure
Frequently asked questions
How many tons of rock do I need for 200 square feet?
About 1.7 tons at 2 inches deep (order 2 tons) or 2.6 tons at 3 inches (order 3 tons).
How deep should landscape rock be?
2 inches minimum for looks, 3 inches for weed suppression. Match depth to stone size — large 2–3-inch river rock wants 3–4 inches.
Should I put landscape fabric under decorative rock?
Yes — woven fabric suppresses weeds while draining. Avoid solid plastic sheeting, which traps water and suffocates the soil.
How is decorative rock sold — by the ton, yard, or bag?
Landscape yards sell by the ton or yard (~1.4 tons per yard for most rock). Home-center 0.5-ft³ bags only make sense for tiny areas — 54 bags make a yard.
Does rock color change how much I need?
No — coverage is by volume and weight regardless of color. But rinse rock after spreading; quarry dust dulls the true shade.
Can I use rock instead of mulch around plants?
Yes, with caveats: rock doesn’t feed the soil, it radiates heat (tough on some plants in hot climates), and fallen leaves are harder to clean out of it than off mulch.