How Much Mulch or Soil Do You Need? Coverage by Depth
September 18, 2026
Cubic Yards = (Length × Width × Depth in feet) / 27. Since depth is part of the formula, doubling your desired mulch depth doubles the amount you need for the same area — a detail that's easy to underestimate when just thinking in square feet.
Skip the math and get your answer instantly:
Open the Mulch & Soil Calculator →Worked Example
A 20×10 ft garden bed with 3 inches (0.25 ft) of mulch: 20 × 10 × 0.25 = 50 cubic feet, ÷ 27 = 1.85 cubic yards.
Recommended Depth by Use Case
| Use Case | Recommended Depth |
|---|---|
| Mulch around trees/shrubs | 2-4 inches |
| Mulch for weed suppression | 3-4 inches |
| Topsoil for new lawn | 4-6 inches |
| Raised garden bed soil | 8-12 inches |
Bags vs. Bulk Delivery
A standard bag of mulch covers about 2 cubic feet. For small areas (under about 2 cubic yards, or 54 cubic feet), bags are usually more convenient. For larger projects, bulk delivery by the cubic yard is typically far more cost-effective per unit volume, despite the upfront delivery logistics.
Frequently Asked Questions
How do I calculate how much mulch I need?
Multiply length × width × depth (all in feet) to get cubic feet, then divide by 27 to convert to cubic yards for bulk ordering.
How deep should mulch be around trees and shrubs?
Typically 2-4 inches — enough to suppress weeds and retain moisture without smothering roots or promoting rot against the trunk.
How many bags of mulch equal a cubic yard?
About 13-14 standard 2-cubic-foot bags equal one cubic yard (27 cubic feet ÷ 2).
Is bulk mulch cheaper than bagged mulch?
Usually yes, per cubic yard, especially for larger projects — bagged mulch carries a convenience premium that adds up quickly beyond a couple of cubic yards.
How much topsoil do I need for a raised garden bed?
For a typical raised bed depth of 8-12 inches, calculate cubic yards the same way: length × width × depth (in feet) ÷ 27, using your bed's actual depth.