Landscape Rock Calculator

How to Use the Landscape Rock Calculator

• Pick the material — the dropdown shows each one's density so you can compare weight-driven cost.
• Enter the area to cover in square feet; break irregular beds into rectangles and add them.
• Set the depth: 2 inches for beds and borders, 3 to 4 for driveways and paths.
• Type the per-ton price your landscape yard quoted — not a per-yard guess.
• Read the tonnage and cost, then round up toward a full delivery minimum.
• Multiply your tonnage by about 1.1 if the site is rough, sloped or spread around obstacles.

The Rock Tonnage Formula, Explained

Worked Example: A 300 sq ft River-Rock Border

• The bed is 300 sq ft and you want a solid 3 inches of river rock.
• Volume: 300 × 3 ÷ 12 = 75 cu ft, which is about 2.8 cu yd.
• River rock runs 105 lb/cu ft, so weight = 75 × 105 = 7,875 lb.
• In tons: 7,875 ÷ 2,000 = 3.94 tons — call the order 4 tons.
• At $90 a ton delivered, the border is roughly $360 of stone.
• The same bed in lava rock would be 75 × 45 ÷ 2,000 = 1.7 tons — but lava at $130/ton still lands near $220, so the light rock saves freight yet costs more per yard.
• That comparison — tonnage against per-ton price against a delivery minimum — is the decision the calculator is built to frame.

Tons per 100 sq ft by Depth

Key Terms

Density (lb/cu ft)

How much a cubic foot of the rock weighs loose — the figure that converts your bed's volume into tonnage and cost.

Ton

2,000 lb; the unit rock is sold and hauled in, which is why weight, not volume, sets the price.

Cubic yard

27 cu ft — the 'yard' trucks are quoted in; useful only once you know the material's density per yard.

Crushed / angular

Rock with sharp faces (drain rock, crusher fines) that locks down for paths and driveways.

Delivered minimum

The smallest load a yard will truck out — often a full 'ton unit' — that rounds your order up regardless of the math.

What This Means at the Landscape Yard

• Buy on the ton and confirm the density: two yards quoting 'gravel' can differ by 20% per cubic foot between dry and damp, and moisture adds real weight to a truck scale.
• Depth is the lever you control: a 2-inch bed uses half the tonnage of a 4-inch one for the same look, so reserve deep rock for drive surfaces and keep decorative borders lean.
• Weed barrier changes nothing in the math but everything in the outcome — rock over fabric holds its color and stays scooped-back in place; rock over soil becomes a no-dig seedbed.
• Freight is often the hidden half of a small order, which is why rounding to a full delivery minimum beats a second half-load later.
• Heavy, smooth river rock needs edging to hold it; light lava can blow out of an open border in a storm, so pair the material with the site's exposure, not just its price.

Common Mistakes & Fixes

• Pricing rock per cubic yard without knowing its density, then watching the tonnage (and the bill) come in far off the estimate.
• Sizing beds at 1 inch to save money — thin rock disappears into weeds and dirt within a season and gets topped up twice.
• Ordering the exact calculator tonnage with no buffer for rough, sloped or obstacle-strewn ground that swallows more material.
• Skipping weed barrier under decorative rock and later hand-picking seedlings out of a border that became a mulch-free seedbed.
• Choosing lava rock for a driveway to save weight, when its light, round pieces crush and shift under tires that angular gravel would lock.

When to Use This (and When Not To)

Landscape Rock Calculator: Frequently Asked Questions