Rock Calculator

Calculate how many tons of rock you need for landscaping, drainage or erosion control. Pick a rock type and size to get tons and cubic yards.

H

Creator

Haali

Updated October 2026

Calculate your rock

Results update as you type

Units
Area to cover
Total area
Length
Width
Rock size
Depth
Material
Density
Bag size
Bag size
Price (optional)
Add 5% for gaps and waste

You need about

Area
Volume
Estimated cost

Enter your measurements above to see how much rock to order.

See all calculators
Related: River Rock Landscape Rock Gravel Stone

Rock or gravel?

Suppliers usually call anything bigger than about 1 inch (25 mm) rock rather than gravel. Bigger pieces need a deeper layer to cover the ground, so they take more tons per square foot.

How deep should rock be?

Lay rock about twice as deep as the stones are wide, so they sit on each other and no soil shows through.

Small rock, 0.75 to 1.5 in (20 to 40 mm) 2 in (5 cm)
Medium rock, 1.5 to 3 in (40 to 75 mm) 4 in (10 cm)
Large rock, 3 to 6 in (75 to 150 mm) 8 in (20 cm)
Riprap for banks, 6 to 12 in (150 to 300 mm) 16 in (40 cm)

What types of rock are there?

Granite

Hard, heavy and long lasting. Comes crushed or as boulders.

Best for paths and edging

Limestone

Pale and affordable. Softer than granite.

Best for drainage and bases

Lava rock

Light and porous. About half the weight of granite.

Best for planters and roof terraces

Riprap

Large, rough rock that holds soil in place.

Best for slopes and stream banks

How does the calculation work?

Tons = area × depth × density

A drainage strip 30 ft by 3 ft with 4 in of rock: 90 ft² × 0.33 ft = 30 ft³, or 1.1 yd³. In granite at about 1.35 tons per cubic yard, that is 1.5 tons.

Before you order

Lay a heavy landscape fabric so weeds cannot grow through.
Check the rock size with your supplier, since names vary between yards.
Large rock and riprap are placed with machinery, so plan access for the truck.
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