Calculating Tumbled Rock Volume and Weed Control for Landscape Beds

Two beds need rock: 50×6 ft and 29×6 ft, both 3 inches deep. The homeowner wants to know how much rock to order, what size to choose, and whether to use weed fabric.

Volume Calculation

Cubic yards = (Length × Width × Depth in feet) ÷ 27

• Bed 1: 50 × 6 × 0.25 = 75 cu ft = 2.78 cu yd
• Bed 2: 29 × 6 × 0.25 = 43.5 cu ft = 1.61 cu yd
• Total: ~4.4 cu yd — order 5 cu yd for compaction and waste.

Rock Size Selection

• ⅜″–½″ (pea gravel): Comfortable to walk, shifts easily.
• ¾″–1″ (river rock/tumbled): Stays put better, good drainage, standard for beds.
• 1½″–2″ (cobble): Bold look, hard to walk on, best for accents.

For planting beds, ¾″–1″ tumbled stone balances aesthetics and stability.

Weed Control: Fabric + Pre-Emergent

Landscape fabric (woven polypropylene) under rock works if:

• Fabric is pinned every 3 ft.
• Seams overlap 12″.
• Rock depth is ≥3″ (blocks light).
• No soil accumulates on top.

Add a pre-emergent herbicide (prodiamine, dithiopyr) in early spring and fall for a second line of defense. Fabric alone fails once fines fill the gaps.

Order 5 cu yd of ¾″ tumbled rock, lay fabric with pins, apply pre-emergent, and enjoy a clean, low-maintenance bed.