How Many Yards of Mulch Do I Need?
Quick answer: cubic yards of mulch = square feet × depth in inches ÷ 324. At a typical 3 in depth, one cubic yard covers 108 sq ft. A 10 × 20 ft bed (200 sq ft) at 3 in needs 200 × 3 ÷ 324 = 1.85 yd³, which is about 25 bags of 2 cu ft. University extension services generally recommend 2–4 in of mulch.
The 324 shortcut works because one cubic yard (27 cu ft) spread 1 inch thick covers 27 × 12 = 324 square feet. Measure each bed, add the areas, and pick a depth. The mulch calculator handles odd shapes, bags, and cost.
Mulch coverage per cubic yard
| Depth | 1 yd³ covers | Yards per 100 sq ft |
|---|---|---|
| 1 in | 324 sq ft | 0.31 |
| 2 in | 162 sq ft | 0.62 |
| 3 in | 108 sq ft | 0.93 |
| 4 in | 81 sq ft | 1.23 |
Bags of mulch per cubic yard
- 2 cu ft bags: 27 ÷ 2 = 13.5 bags per cubic yard
- 3 cu ft bags: 27 ÷ 3 = 9 bags per cubic yard
- 1.5 cu ft bags: 27 ÷ 1.5 = 18 bags per cubic yard
Bulk mulch is usually cheaper than bags once you need more than 2–3 cubic yards. Compare the delivered price per cubic yard.
How deep should mulch be?
Extension services, including the University of Minnesota, recommend 2–4 inches. That is deep enough to block weeds and hold moisture without smothering roots. The University of Illinois suggests 2–3 in for fine materials like compost and 3–4 in for coarse wood mulch. Oregon State warns that more than 4 in can cut off oxygen to roots. Keep mulch a few inches away from tree trunks and plant stems.
When you top up an existing bed, measure what is left. Often 1–2 in of fresh mulch is enough to get back to 3 in.
Worked examples
- Foundation bed, 3 × 40 ft (120 sq ft) at 3 in: 120 × 3 ÷ 324 = 1.11 yd³, or about 15 bags of 2 cu ft.
- Tree ring, 6 ft wide (28.3 sq ft) at 3 in: 28.3 × 3 ÷ 324 = 0.26 yd³, or about 4 bags of 2 cu ft.
- Large bed, 20 × 30 ft (600 sq ft) at 3 in: 600 × 3 ÷ 324 = 5.6 yd³. Order bulk.
Frequently asked questions
How much area does a yard of mulch cover?
One cubic yard covers 324 sq ft at 1 in deep, 162 sq ft at 2 in, 108 sq ft at 3 in, and 81 sq ft at 4 in.
How many bags of mulch are in a yard?
13.5 bags of 2 cu ft, 9 bags of 3 cu ft, or 18 bags of 1.5 cu ft make one cubic yard.
How deep should I spread mulch?
Most extension services recommend 2–4 inches: thinner for fine mulch and compost, thicker for coarse wood chips. Avoid going deeper than 4 inches and keep mulch off trunks and stems.
How much mulch do I need for 100 square feet?
About 0.93 cubic yards at 3 in deep, roughly 13 bags of 2 cu ft. At 2 in deep it is 0.62 yards, about 9 bags.
How much does a yard of mulch weigh?
Mulch is light. Weight varies widely with wood type and moisture; our calculators use about 0.55 tons (1,100 lb) per cubic yard as a planning figure.
Related calculators and guides
Sources
- University of Minnesota Extension: Mulching for soil and garden health
- University of Illinois Extension: Proper mulching techniques
- Oregon State University Extension: Waterwise gardening in Central Oregon
Updated: October 17, 2026 by the YardsCalculator editorial team. Figures are planning estimates; confirm weights, truck capacity, and prices with local suppliers and haulers.