Measure the rock-covered area, then set the finished depth
A bed’s square footage is its length times its average width. For a curved border, measure its width in several places and average those readings, or split it into smaller rectangles and add their areas. Subtract large paved sections and plant islands that will stay bare.
Use the depth you want after spreading. A 2–3 inch layer is a useful starting point for inorganic mulch, but a larger stone may leave visible gaps at the shallow end. Spread a small test patch with your chosen rock before you commit to a truckload.
From bed dimensions to the order quantity
The calculator converts square feet and inches into cubic yards, then uses the selected bulk density to estimate short tons. The allowance is added to volume before converting to tons and bags.
40 ft × 8 ft = 320 sq ft
320 × 3 in ÷ 324 = 2.96 yd³
2.96 yd³ × 1.10 = 3.26 yd³, or 4.40 short tons at 1.35 t/yd³
The same example fills 176 bags at 0.5 cu ft each: 320 × (3 ÷ 12) × 1.10 ÷ 0.5. A bag marked only in pounds needs its own volume or coverage figure.
Choose the rock for the bed, not just the color
Rounded river rock
A smooth finish suits broad borders and dry stream accents. Rounded pieces move more easily at an open edge or on a slope, so plan for containment and assess drainage. For a dedicated estimate, use the river rock calculator.
Angular crushed stone
Angular pieces tend to nest together more firmly than rounded stone. The actual bulk weight depends on grading and source. Compare options in the crushed stone calculator. For a path or patio base, the landscape stone calculator separates finished depth from loose order volume.
Porous lava rock
Lava rock can be much lighter by volume than dense natural stone. Its porosity and piece size vary, so treat the preset density as a starting estimate. See the lava rock calculator for that material.
A rock bed still needs a planting and maintenance plan
Decide whether fabric helps here
Permeable landscape fabric can keep rock from mixing into soft soil. It is less convenient in beds you replant often, and weeds can establish in dust and leaves above it. Do not rely on solid plastic as a universal weed fix; it restricts water and air movement. Read the rock-bed weed guide and the stone-sinking guide.
Protect plants and bed edges
Keep stone a few inches clear of woody stems and root collars. Check the site’s sun exposure: rock can warm the soil in summer, which may matter around heat-sensitive plants. Remove leaf litter before it turns into a growing medium for weeds. For installation details, see how to install landscape rock.
Confirm the purchase unit
Bring your yardage, chosen stone, and target depth to the supplier. Ask whether they sell by cubic yard or short ton and what bulk density they use. The calculator’s three rock presets are estimates; replace the density with the supplier’s figure when available. For a broader depth comparison, see the rock depth guide.
Landscape rock coverage examples
These figures use 1.35 short tons per cubic yard and 0.5-cu-ft bags, with no added allowance. Your supplier’s density and packaging can differ.
| Bed area | Depth | Cubic yards | Short tons | 0.5-cu-ft bags |
|---|---|---|---|---|
| 100 sq ft | 2 in | 0.62 | 0.83 | 34 |
| 100 sq ft | 3 in | 0.93 | 1.25 | 50 |
| 250 sq ft | 3 in | 2.31 | 3.13 | 125 |
| 500 sq ft | 3 in | 4.63 | 6.25 | 250 |
Landscape rock questions
How much landscape rock do I need for 500 square feet?
At a 3-inch finished depth, 500 square feet needs 4.63 cubic yards before any extra material. A 10% allowance brings the order estimate to 5.09 cubic yards. At an assumed bulk density of 1.35 short tons per cubic yard, that is about 6.88 short tons. Confirm the density with your supplier.
How deep should landscape rock be in a planting bed?
Two to three inches is a useful starting range for many inorganic mulches. The right depth also depends on the stone size, desired coverage, plants, and site. Test a small area before ordering, especially when individual stones are nearly as thick as the planned layer.
Does landscape fabric keep a rock bed weed-free?
No. Permeable fabric can separate stone from soil and reduce some weeds, but windblown soil and seeds can collect above it. Fabric can also complicate planting and later changes. Remove new weeds and leaf debris before they become established.
Can I calculate bag count from a 50-pound bag label?
Not reliably. This calculator counts 0.5-cubic-foot bags by volume. Bags sold only by weight cover different volumes depending on the stone and packing; check the bag’s cubic-foot coverage or ask the seller.