Mulch Calculator
Calculate cubic yards and bags of mulch for garden beds and landscaping.
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How to Calculate Mulch for Garden Beds
The mulch calculator helps you buy the right amount of mulch for your garden beds and landscaping. Mulch depth matters — too little doesn't suppress weeds, too much can harm plants. This calculator gives both bulk cubic yards and bag counts so you can choose the most economical option.
The Formula
Cubic yards = length × width × (depth in inches) ÷ 324. The number 324 = 12 inches/ft × 27 cu ft/cu yd. For a 20×10 ft bed at 3-inch depth: 20 × 10 × 3 ÷ 324 = 1.85 cubic yards. Round up to 2 cubic yards for bulk delivery, or divide by bag size (27 ÷ bag size) per yard = number of bags needed.
Bulk vs. Bagged
Bulk mulch delivered by the cubic yard: $30–$50 per yard, minimum delivery 2–3 yards typically. Bagged mulch (2 cu ft bags): $4–$8 per bag = $54–$108 per cubic yard equivalent. Bulk is far more economical for projects over 3 cubic yards. Bagged is convenient for small projects and precise top-up applications.
Recommended Depths
2 inches: light top-up for existing mulched beds. 3 inches: standard depth for new beds — good weed suppression and moisture retention. 4 inches: maximum for established plants (avoid against stems). 6 inches: playground safety surfacing per ASTM F1292 fall safety standards.
Benefits of Mulching
A proper 3-inch mulch layer retains soil moisture (reducing irrigation by 25–50%), suppresses weeds, moderates soil temperature swings, prevents soil compaction, adds organic matter as it decomposes, and gives garden beds a neat, finished appearance. For most beds, spring mulching is the most important single landscaping task.
Frequently Asked Questions
Use: sq ft × depth (in inches) ÷ 324 = cubic yards. For 200 sq ft at 3 inches: 200 × 3 ÷ 324 = 1.85 cu yd. Round up to 2 cu yd for bulk delivery.
3 inches is the standard recommendation. Less than 2 inches won't suppress weeds well. More than 4 inches can prevent rain from reaching roots and may promote fungal problems. Keep mulch 2–3 inches away from plant stems and tree trunks.
One cubic yard = 27 cubic feet. At 2 cu ft/bag: 14 bags per yard. At 3 cu ft/bag: 9 bags per yard. Bulk mulch is typically 30–50% cheaper than bagged for equivalent volume.
Spring, after the soil has warmed up. Mulching too early traps cold and delays soil warming. Fall mulching is beneficial for protecting plant roots from temperature extremes but can provide winter cover for pests. Pull back mulch slightly in late winter to let soil warm for spring planting.
Wood mulch near your home's foundation can create favorable conditions for termites and other wood-destroying insects. Keep mulch at least 6 inches away from your home's foundation wall. Use inorganic mulch (gravel, rubber) near the house if termites are a concern in your area.