Mulch & Gravel Calculator
Calculate how much mulch, gravel, or topsoil you need for a bed, path, or driveway — in cubic yards and bags.
How this calculator works
Volume = Area × Depth. Area is your length × width in square feet; depth is entered in inches and converted to feet (divided by 12) so the units match. The result in cubic feet is divided by 27 to get cubic yards, which is how bulk mulch, gravel, and topsoil are typically sold and delivered.
For bagged material, the same cubic-foot volume is divided by the coverage of one bag — a standard mulch bag covers 2 cubic feet, a gravel bag is often 0.5 cubic feet, and topsoil bags vary (this calculator lets you set the exact bag size).
Example calculation
Project: a 20 ft × 10 ft garden bed, 3 inches of mulch depth.
- Area = 20 × 10 = 200 ft²
- Volume = 200 × (3 ÷ 12) = 50 ft³
- Cubic yards = 50 ÷ 27 ≈ 1.85 yd³
- 2 ft³ bags needed = 50 ÷ 2 = 25 bags
At around $40 per cubic yard delivered in bulk, that’s roughly $74 — usually cheaper than buying 25 individual bags once you’re covering more than a couple hundred square feet.
Buying & material guidance
Mulch depth of 2–3 inches is standard for garden beds — more than 4 inches can suffocate roots and promote fungal growth. Gravel for pathways is usually 2 inches deep over landscape fabric; driveways need 4–6 inches in multiple compacted layers. Topsoil for new lawns or beds is typically 4–6 inches.
Bulk delivery is almost always cheaper than bags once you need more than about 1 cubic yard (roughly 13–14 bags of mulch), and saves you from hauling dozens of heavy bags yourself.
Frequently asked questions
How much mulch do I need for 200 square feet?+
At a standard 3-inch depth, 200 square feet needs about 1.85 cubic yards of mulch, or roughly 25 bags if using 2-cubic-foot bags.
How deep should mulch be?+
2 to 3 inches is the standard recommendation for garden beds. Going deeper than 4 inches can suffocate plant roots and encourage fungal problems.
Is it cheaper to buy mulch or gravel in bulk or bags?+
Bulk delivery is typically cheaper once you need more than about 1 cubic yard (roughly 13-14 standard bags). For smaller areas, bagged material is often more convenient despite the slightly higher per-yard cost.