Enter the length, width and depth of the bed or border. Pick the rock type and the ticket gives you tons, cubic yards and bags, with a drawing to check against.

How deep to lay landscape rock

Stone size	Depth
Small stone, ½ in or less (pea gravel)	2 in
Medium stone, 1–2 in (river rock, basalt)	3–4 in
Large stone, 3 in and up (cobbles)	5–6 in

From SelectSG. Their rule of thumb: lay rock at least twice as deep as the stone is wide, so the ground or fabric doesn't show through.

How much area a ton of river rock covers

Depth	One ton covers	One cubic yard covers
2 in	116 ft²	162 ft²
3 in	77 ft²	108 ft²
4 in	58 ft²	81 ft²
6 in	39 ft²	54 ft²

River rock for common sizes

Cubic yards and tons at 1.4 tons per yard, before any extra.

Area	2 in deep	3 in deep	4 in deep
3 × 20 ft	0.37 yd³ · 0.5 t	0.56 yd³ · 0.8 t	0.74 yd³ · 1.0 t
5 × 20 ft	0.62 yd³ · 0.9 t	0.93 yd³ · 1.3 t	1.23 yd³ · 1.7 t
10 × 10 ft	0.62 yd³ · 0.9 t	0.93 yd³ · 1.3 t	1.23 yd³ · 1.7 t
10 × 20 ft	1.23 yd³ · 1.7 t	1.85 yd³ · 2.6 t	2.47 yd³ · 3.5 t
20 × 20 ft	2.47 yd³ · 3.5 t	3.70 yd³ · 5.2 t	4.94 yd³ · 6.9 t

Worked examples

Border along a house, 40 × 3 ft, 3 in of river rock: 1.11 yd³, about 1.6 tons or 60 bags of 0.5 ft³.
Dry creek bed, 30 × 2 ft, 4 in: 0.74 yd³, about 1.0 tons. Add larger cobbles along the edges as separate pieces.
Rock bed, 12 × 10 ft, 3 in: 1.11 yd³, about 1.6 tons.

Weight by rock type

Type	Tons per yd³	Typical range	Yards per ton
River rock	1.4	1.39–1.7	0.71
Pea gravel	1.4	1.35–1.7	0.71
Gravel / crushed stone (¼–2 in)	1.4	1.35–1.7	0.71
Crushed limestone	1.32	1.32–1.7	0.76
Decomposed granite	1.35	1.3–1.4	0.74

Landscape yards usually sell rock by the ton. If yours gives a weight per yard, type it into “Weight per volume” and the ticket uses it.

The formula

Cubic yards = length (ft) × width (ft) × depth (in ÷ 12) ÷ 27
Tons = cubic yards × tons per cubic yard

For round beds, area = 3.14 × radius². For curved borders, measure along the middle of the curve. See the gravel calculator for driveways and paths.

Questions

How much rock do I need?

Multiply length × width (ft) × depth (in ÷ 12) and divide by 27 for cubic yards, then multiply by the rock's weight per yard for tons. A 10 × 20 ft bed of river rock at 3 in is 1.85 yd³, about 2.6 tons.

How deep should landscape rock be?

SelectSG suggests 2 in for small stone, 3–4 in for 1–2 in river rock and 5–6 in for large cobbles, and at least twice the stone size so no gaps show.

How many square feet does a ton of river rock cover?

About 77 ft² at 3 in deep and 58 ft² at 4 in, at 1.4 tons per cubic yard.

How much does a yard of river rock weigh?

About 1.4 tons, with 1.39–1.7 typical. Bigger, rounder stone leaves more gaps; wet stone weighs more.

Do I need landscape fabric?

It is common under rock beds. SelectSG notes that a layer of about 3 in holds the fabric down and keeps light off it; thinner layers can shift and expose it.

How many bags of rock make a yard?

Fifty-four 0.5 ft³ bags. Bagged decorative rock is often sold in 0.5 ft³ bags, but check the bag; past about a cubic yard, bulk is usually cheaper.

See also: Gravel calculator · Tons to yards

Sources

Depth by stone size and fabric: SelectSG, how deep should decorative rock be. Rock weights: SelectSG, Aggregate Markets, Inch Calculator.

Rock Calculator