Calculate how many yards of loam you need for a lawn or garden bed from its size or square feet and depth, with a 10% extra allowance, weight and cost.
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Yards of Loam Formula
- A = area in square feet: length × width for rectangular beds, or π × (diameter/2)² for round beds
- d = finished loam depth in inches; V = net cubic yards
- 324 = conversion factor (12 in/ft × 27 ft³/yd³)
The formula assumes uniform finished depth. The default extra-volume allowance is 10%, adjustable from 0% to 100%; this is a planning assumption, not a measured compaction or shrinkage rate. Order volume equals net volume multiplied by one plus the allowance fraction. Confirm the allowance with your supplier.
Loam Depth and Coverage Reference
The depths below are illustrative project examples, not universal soil specifications. Confirm the appropriate depth for your site, then use the geometric coverage table.
| Project | Illustrative Depth |
|---|---|
| Lawn topdressing | 0.25 in |
| Overseeding cover | 0.5 in |
| Grading low spots | 1–2 in |
| Garden bed amendment | 2–3 in |
| New lawn install | 4–6 in |
| Raised bed fill | 8–12 in |
| Depth | Coverage per Cubic Yard |
|---|---|
| 0.25 in | 1,296 sq ft |
| 1 in | 324 sq ft |
| 2 in | 162 sq ft |
| 3 in | 108 sq ft |
| 4 in | 81 sq ft |
| 6 in | 54 sq ft |
Example and Common Questions
Example: A new lawn area is 30 ft by 20 ft and you want 4 inches of loam. Area = 600 sq ft. Cubic yards = (600 × 4) / 324 = 7.41 yd³. The 10% extra-volume estimate is about 8.1481 yd³. Follow supplier ordering increments; rounding upward to tenths gives 8.2 yd³.
How much does a yard of loam weigh? The optional planner retains illustrative ranges of 2,000–2,500 lb/yd³ for its screened scenario and 2,500–3,000 lb/yd³ for its wet/heavy scenario. These are assumptions; actual bulk density varies. Obtain your supplier’s density for a real load.
Will a yard fit in a pickup? Check the exact vehicle’s loading label and applicable axle, tire, and gross-weight limits. Occupants, equipment, and other cargo use payload capacity. A volume-only load estimate cannot determine safe vehicle loading; confirm weight and delivery arrangements with the supplier.
Why add a buffer? Loam settles after watering and you lose volume to uneven ground, edging, and spillage during spreading. The default 10% allowance is illustrative and may be insufficient or excessive for a particular site. It adds 10% to net volume; it does not compensate exactly for 10% volume shrinkage.
Loam vs. topsoil: Loam is a soil texture (balanced sand, silt, and clay). Screened loam sold in bulk is the standard product for lawns and gardens. Generic “topsoil” varies in quality.
