Soil, mulch, compost, and fill dirt are sold by the cubic yard (27 cubic feet). To order the right amount, you need to convert your area (in square feet) and desired depth (in inches) into cubic yards.
The formula:
Example: 200 sq ft area, 4 inches deep. Volume = 200 × (4/12) = 200 × 0.333 = 66.67 cubic feet. Cubic yards = 66.67 ÷ 27 = 2.47 cu yd. With 10% for settling: 2.72 cubic yards → order 3 yards.
One cubic yard fills a space approximately 3 ft × 3 ft × 3 ft — about the size of a washing machine. Visualizing this helps with ordering: a small raised garden bed (4 × 8 ft filled to 12 inches deep) needs exactly 1.19 cubic yards — typically ordered as 1.5 yards to account for the soil compacting after watering.
Why soil settles: Loose, freshly delivered soil contains a significant amount of air space. Once applied, watered, and walked on, soil compacts and loses 10–20% of its initial volume. For topdressing (thin layers under 2 inches), settlement is minimal. For deep fills (8+ inches), plan for 15–20% more material to reach your finished grade.
How many cubic yards of soil you need for common project sizes and depths:
| Area (sq ft) | 2 inches deep | 4 inches deep | 6 inches deep | 12 inches deep |
|---|---|---|---|---|
| 50 sq ft | 0.31 cu yd | 0.62 cu yd | 0.93 cu yd | 1.85 cu yd |
| 100 sq ft | 0.62 cu yd | 1.23 cu yd | 1.85 cu yd | 3.70 cu yd |
| 200 sq ft | 1.23 cu yd | 2.47 cu yd | 3.70 cu yd | 7.41 cu yd |
| 500 sq ft | 3.09 cu yd | 6.17 cu yd | 9.26 cu yd | 18.52 cu yd |
| 1,000 sq ft | 6.17 cu yd | 12.35 cu yd | 18.52 cu yd | 37.04 cu yd |
| 2,500 sq ft | 15.43 cu yd | 30.86 cu yd | 46.30 cu yd | 92.59 cu yd |
Values above do not include the 10% settlement factor — add 10–15% for final order quantities. For bulk delivery, most suppliers sell by the cubic yard with a minimum order of 1–2 yards; some offer half-yard pricing. For small quantities (under 1 yard), consider bagged soil from a home improvement store — typically 0.5 to 1.5 cubic feet per bag, priced at a significant premium per yard but no delivery charge.
| Project | Recommended Depth | Notes |
|---|---|---|
| Lawn topdressing | 1/4 – 1/2 in | Thin layer for overseeding; too deep smothers grass |
| Lawn renovation (bare spots) | 2 – 4 in | Loosen existing soil first; blend with existing grade |
| New lawn (sod) | 4 – 6 in | Minimum for healthy turf root development |
| New lawn (seeding) | 6 – 8 in | Deeper topsoil produces denser turf |
| Annual flower bed | 6 – 8 in | Shallower roots; more depth doesn't help |
| Perennial bed | 8 – 12 in | Deeper roots benefit from more prepared soil |
| Vegetable garden | 12 – 18 in | Deep-rooted vegetables (tomatoes, carrots) need depth |
| Raised garden bed | 8 – 12 in | Full 12 in if bottom is sealed; can be less if open to ground |
| Tree planting | Do not add deep soil over existing grade | Raising grade can kill trees by smothering roots |
| Mulch (landscape) | 2 – 4 in | 3 in is optimal; more than 4 in is counterproductive |
Not all soil products are appropriate for all uses. Understanding the differences helps you order the right material the first time:
| Product | Description | Best Use | Cost Range |
|---|---|---|---|
| Topsoil | The upper layer of native soil; quality varies widely | General fill, lawn establishment | $15–$50/yd |
| Garden soil | Amended topsoil with compost added | Planting beds, gardens | $30–$80/yd |
| Compost | Decomposed organic material, nutrient-rich | Amendment, raised beds, topdressing | $30–$60/yd |
| Fill dirt | Subsoil without organic matter; may contain clay or rocks | Grade changes, foundation fill, never for planting | $5–$25/yd |
| Potting mix | Lightweight blend for containers; no actual soil | Containers, raised beds only | $40–$100/yd |
| Sandy loam | Balanced texture; drains well with some water retention | Lawn base, all-purpose planting | $20–$45/yd |
| Triple mix | Topsoil + compost + peat (1:1:1) | Premium planting, high-value gardens | $40–$80/yd |
The fill dirt warning: Never use fill dirt in planting areas. Fill dirt is subsoil — below the biological zone where organic matter and microbial life exist. It often contains high clay content, compacts severely, drains poorly, and supports almost no plant life. If you need to change grade and then plant, use fill dirt for the bulk of the elevation change and cap with 6–8 inches of topsoil or garden soil at the surface.
Raised garden beds are one of the most common soil calculation scenarios. Here's how to calculate soil for standard raised bed dimensions:
| Bed Size | Depth 6 in | Depth 8 in | Depth 12 in |
|---|---|---|---|
| 4 × 4 ft (16 sq ft) | 0.30 cu yd | 0.40 cu yd | 0.59 cu yd |
| 4 × 8 ft (32 sq ft) | 0.59 cu yd | 0.79 cu yd | 1.19 cu yd |
| 4 × 12 ft (48 sq ft) | 0.89 cu yd | 1.19 cu yd | 1.78 cu yd |
| 4 × 16 ft (64 sq ft) | 1.19 cu yd | 1.58 cu yd | 2.37 cu yd |
| 3 × 6 ft (18 sq ft) | 0.33 cu yd | 0.44 cu yd | 0.67 cu yd |
For raised bed soil, professionals recommend the "Mel's Mix" (Square Foot Gardening): 1/3 blended compost + 1/3 peat moss + 1/3 coarse vermiculite. This mix is lightweight, drains perfectly, never compacts, and provides excellent fertility. For a 4×8 ft bed at 12 inches deep (1.19 cubic yards), you'd need approximately 0.4 cu yd of each component.
If buying bags rather than bulk: standard 1.5 cubic foot bags of potting mix or garden soil. To fill one cubic yard, you need 18 bags (27 ÷ 1.5 = 18). For a 4×8 bed at 12 inches (1.19 yards), that's approximately 21–22 bags — which can add up quickly in cost versus bulk delivery.
Mulch calculations follow the same formula as soil, but the optimal depth is much more specific — and this is one area where more is genuinely counterproductive:
Annual refresh: Organic mulch decomposes over time, which is actually beneficial — it adds organic matter to the soil. Refresh mulch annually by adding 1–1.5 inches on top of the remaining old mulch, rather than removing and replacing all mulch each year. Constant removal and replacement depletes the organic matter benefit and wastes money.
For a 10×10 ft (100 sq ft) garden at 6 inches deep: 100 × (6/12) = 50 cubic feet ÷ 27 = 1.85 cubic yards. Add 10% for settlement: 2.04 yards → order 2 yards. At 12 inches deep: 3.70 cubic yards → order 4 yards.
It depends on bag size: A 1 cubic foot bag takes 27 bags per yard. A 1.5 cubic foot bag (most common at home improvement stores) takes 18 bags per yard. A 2 cubic foot bag takes 13.5 bags per yard. Bulk delivery from a landscape supplier typically costs 30–50% less per cubic yard than bagged soil once you need more than 1–2 cubic yards.
Topsoil is the biologically active upper layer of soil (typically 6–12 inches in nature) containing organic matter, nutrients, and microorganisms. Fill dirt is subsoil — below the topsoil layer — with little or no organic content. Fill dirt compacts tightly and is used for grading and structural fill. Never use fill dirt in planting areas; always cap with topsoil.
For a new lawn from seed or sod, add a minimum of 4 inches of topsoil — 6 inches is better for superior turf quality. Loosen the existing soil 2–3 inches deep before adding the new topsoil so the roots can penetrate the transition zone. Compacted or abruptly different soil layers create a "perched water table" where roots stop growing at the interface.
A standard 1/2-ton pickup truck bed holds approximately 1 to 1.5 cubic yards of soil — roughly 1,500–2,000 lbs (at ~1,200 lbs per cubic yard for topsoil). A full-size 3/4-ton or 1-ton truck can safely carry 2 cubic yards. Overloading damages the truck suspension and creates unsafe driving conditions. For more than 2 yards, use a trailer or arrange bulk delivery.
The quantity of soil matters, but the quality determines whether your planting will succeed. Understanding what to add — and how much — is the difference between thriving plants and chronic struggling:
The soil triangle: Ideal garden soil is 40–45% mineral particles, 5% organic matter, 25% air, and 25% water. Sand, silt, and clay particles come in different proportions depending on your native soil type. Sandy soils drain quickly and are easy to work but retain little water or nutrients. Clay soils retain water and nutrients but drain poorly, compact easily, and are difficult to work. The ideal "loam" is a balanced blend of sand, silt, and clay with good structure.
Improving clay soil: Adding compost is the best long-term strategy. Incorporate 2–3 inches of compost into the top 6–8 inches of clay soil before planting. Avoid the common mistake of adding sand to clay — unless you add enough sand to fundamentally change the texture (usually 50%+ sand by volume), the result is something closer to concrete than loam. Compost also introduces the biological activity that creates soil structure (aggregation) over time.
Improving sandy soil: Sandy soil's main problems are rapid water drainage and poor nutrient retention. The solution is organic matter — compost, well-aged manure, or peat moss. Adding 3–4 inches of compost to sandy soil dramatically improves moisture retention. Sandy soils also benefit from humic acid amendments, which improve nutrient holding capacity (cation exchange capacity, or CEC). In desert-adjacent climates, biochar mixed into sandy soil can permanently improve water retention.
Soil pH and nutrient availability: Most vegetables and ornamentals prefer a soil pH of 6.0–7.0. Outside this range, nutrients may be present in the soil but become chemically unavailable to plants — this is why plants can show nutrient deficiency symptoms in fertile soil. Test your soil pH (inexpensive DIY kits or through a university extension service) before investing in expensive soil amendments. Acidic soil (pH < 6.0) is treated with lime; alkaline soil (pH > 7.5) is treated with elemental sulfur or acidifying fertilizers.
How much compost to add: For establishing new planting beds, incorporate 3–4 inches of compost into the top 8–10 inches of soil — this represents roughly 30% compost by volume in the planting zone. For annual topdressing of established beds, apply 1–2 inches per year. Over 3–5 years of consistent compost addition, even poor clay or sandy soil transforms into productive garden soil with good structure, drainage, and fertility.
One cubic yard of quality compost covers a 100 sq ft garden bed to approximately 3 inches deep — the ideal amendment rate for improving problem soils. Ordering compost with your topsoil at the same time often saves on delivery charges and allows you to mix on-site before filling raised beds or incorporating into existing soil.