How Much Mulch Do I Need?
Mulch quantity depends on the bed area and the desired depth. Here's the calculation.
Step 1: Measure Bed Area
For a rectangular bed, multiply length × width:
Area = length × width (sq ft)
A 10 × 5 ft bed = 50 sq ft.
Step 2: Choose Depth
Mulch depth depends on the application:
- 2 inches: Annual top-dressing over existing mulch
- 3 inches (default): Standard for new beds — suppresses weeds without suffocating plants
- 4 inches: Weed suppression on bare soil
- 6 inches: Playground or pathway mulch
Avoid piling mulch deeper than 4 inches around plant stems — it causes rot.
Step 3: Calculate Volume
Convert depth from inches to feet, then multiply:
Volume (cu ft) = area × (depth ÷ 12)
50 × (3 ÷ 12) = 12.5 cu ft.
Step 4: Convert to Bags or Cubic Yards
Bags = ceil(volume ÷ bag size)
With 2 cu ft bags: ceil(12.5 ÷ 2) = 7 bags.
Cubic yards = volume ÷ 27
12.5 ÷ 27 = 0.46 cu yd (for bulk delivery).
Bagged vs Bulk
For beds under 2 cubic yards (27 bags at 2 cu ft), bagged is convenient. For larger areas, bulk delivery by the cubic yard is 40-60% cheaper. Most suppliers have a 1-2 cubic yard minimum for delivery.
Quick Coverage Reference (2 cu ft bags)
| Depth | Coverage per Bag | Bags per 100 sq ft |
|---|---|---|
| 2" | 12 sq ft | 9 |
| 3" | 8 sq ft | 13 |
| 4" | 6 sq ft | 17 |
Use the Calculator
The Mulch Calculator handles all of these steps — enter bed dimensions, depth, and bag size for instant results. For soil (growing medium), use the Topsoil Calculator — mulch and topsoil have different densities and depths.