Topsoil is the natural upper layer of earth—mineral soil, some organic matter, and whatever is native to your site. It is for filling, grading, and leveling. Garden soil is a blended product with added compost, fertilizers, and other amendments designed to support plant growth. Use the wrong one and you will either plant in dead dirt or pay premium prices to fill a low spot.
The Key Differences
| Property | Topsoil | Garden Soil | Potting Mix |
|---|---|---|---|
| Composition | Mineral soil + minor organic matter | Topsoil + compost + amendments | Peat/coir + perlite + bark (no true soil) |
| Drainage | Variable (depends on clay/sand ratio) | Moderate—improved over straight topsoil | Excellent |
| Nutrient content | Low | Medium | Low to medium (often fertilized) |
| Best use | Grading, filling, lawn establishment | In-ground planting beds | Containers, raised beds |
| Not suitable for | Container plants (compacts) | Large filling/grading jobs (too costly) | In-ground planting (drains too fast) |
| Cost (bulk) | $15–$35/yd³ | $25–$55/yd³ | $60–$100/yd³ equivalent |
| Cost (bagged) | $3–$5/40-lb bag | $5–$8/1-cu-ft bag | $8–$15/1-cu-ft bag |
When to Use Topsoil
Topsoil is the right choice whenever you are moving large volumes of earth:
Lawn leveling and new lawn establishment. Spread 4–6 inches of screened topsoil, grade and rake, then seed or sod. This is the most common large-scale topsoil use. The Virginia Cooperative Extension recommends a minimum 4-inch topsoil layer for residential lawns.
Grading around foundations. New construction sites often strip and export native topsoil. Backfilling and grading away from the foundation requires cheap fill—topsoil works but straight fill dirt is even cheaper for the lowest layers.
Raising beds before planting. If you need to raise a planting area 4+ inches, use topsoil as the base and garden soil or compost on top 3–4 inches.
How Much Topsoil Do You Need?
Formula: Length × Width × Depth (in feet) ÷ 27 = cubic yards
Worked example—500 sq ft lawn at 4 inches:
- 500 × (4/12) ÷ 27 = 6.2 cubic yards
- Add 10% for settling = 6.8 cubic yards
- At $28/yd³ delivered: ~$190 in material
Use the topsoil calculator to handle this conversion and add a delivery distance factor.
When to Use Garden Soil
Garden soil (also called “premium garden mix” or “planting mix”) makes sense when you are improving a planting area and plant performance is the priority:
In-ground vegetable and flower beds. Till 4–6 inches of garden soil into the existing native soil to improve drainage and fertility.
Over existing lawn for a new bed. Spread 3–4 inches of garden soil over the surface and plant directly into it. This lasagna-method approach avoids tilling and preserves soil structure.
Topping off raised beds. A raised bed that has settled 3–4 inches benefits from fresh garden soil—do not use straight topsoil or the bed will compact.
The Bagged Soil Trap
Big-box store “topsoil” bags (40 lbs, ~0.75 cu ft) are notoriously inconsistent. Some contain good screened mineral soil; others are mostly peat or poorly composted organic matter. The label “topsoil” in bags has no regulatory standard. Check the bag for clumping, smell it for sourness, and read the ingredient list.
For any project requiring more than 5–6 cubic yards, ordering bulk topsoil from a landscape supply company is always cheaper and usually better quality.
Bag equivalent: 1 cubic yard = 27 cubic feet. A standard 40-lb bag of topsoil is roughly 0.5–0.75 cubic feet. You need 36–54 bags to equal one cubic yard. At $4/bag, that is $144–$216 per yard—versus $25–$40/yd³ in bulk.
Can You Make Your Own Amended Topsoil?
Yes. Many experienced gardeners buy bulk topsoil and mix in bulk compost at home:
- 2/3 screened topsoil + 1/3 bulk compost makes an excellent in-ground planting medium
- For raised beds, a soilless approach often works better—see raised-bed-soil-mix
For calculating volumes of amendments, the topsoil calculator and raised-bed-soil-calculator can both handle mixed-ingredient totals.
How to Test Your Existing Soil Before Buying
Before ordering topsoil or garden soil, dig down 6 inches in a few spots and examine what you already have:
- Crumbly, dark brown, earthy-smelling: You likely have good topsoil. Amend with compost only.
- Grey or orange-red, slick when wet: Heavy clay. You need significant amendment—add topsoil plus compost and till deeply.
- Sandy, drains immediately: Low nutrient-holding capacity. Add topsoil and compost to improve retention.
- Full of rocks or gravel: May signal disturbed fill from construction. Adding topsoil is the right move.
A basic soil test from your state’s cooperative extension service (usually $15–$25) tells you pH, nutrient levels, and organic matter content. This prevents the mistake of adding nutrients the soil already has, or fixing the wrong problem with expensive amendments.
Topsoil Delivery: What to Expect
Bulk topsoil is typically delivered by dump truck. Most suppliers have a 1–3 yard minimum order. Specify:
- Screened vs. unscreened: Screened topsoil ($5–$10/yd³ more) is worth it for lawn work; unscreened is fine as fill under a deck or structure.
- Organic matter content: Ask for topsoil with at least 3–5% organic matter for lawn and bed applications.
- Delivery window: Coordinate so the pile can be spread quickly—topsoil kills grass in a week if left in a pile.
Fill Dirt vs. Topsoil: Know the Difference
If you are filling a large low spot, raising a grade, or building up a slope, you do not need to pay topsoil prices for the entire depth. Fill dirt (also called fill soil or bank-run gravel) is unscreened material from construction excavations—it typically costs $5–$15 per cubic yard, far less than topsoil at $20–$35 per cubic yard.
Best practice for deep fills:
- Fill the lower 6–8 inches with compacted fill dirt or clean fill
- Add 4–6 inches of screened topsoil on top for the growing zone
- Seed, sod, or plant into the topsoil layer only
This layered approach can cut material costs by 50–70% on large grading projects. Ask local excavators or construction companies about fill dirt—they often give it away for free or at minimal cost to avoid disposal fees.
Soil pH and Nutrient Availability
Both topsoil and garden soil perform best in the pH range of 6.0–7.0 for most plants and grasses. Outside this range, nutrients become less available to roots even if the soil is otherwise rich.
Regional pH baselines:
- Eastern US soils: often acidic (5.5–6.5). Add ground limestone to raise pH toward 6.5.
- Midwestern soils: often near neutral (6.5–7.0). Minimal amendment usually needed.
- Western and arid soils: often alkaline (7.0–8.5). Add sulfur to lower pH for acid-loving plants.
A basic soil test ($15–$25 from your state extension service) tells you current pH and nutrient levels before you spend money on amendments. Testing first prevents the common mistake of adding lime when the soil is already alkaline, which can lock out micronutrients and harm plants.
Common Mistakes
Using straight topsoil in raised beds. Topsoil compacts under repeated watering and foot traffic near the bed—within one season it can become hard and hydrophobic. Always amend with compost (at least 30%) or use a purpose-built raised-bed mix. See raised-bed-soil-mix for the standard recipe.
Buying topsoil based only on color. Dark color in a topsoil bag can indicate peat or dyed material, not necessarily high organic matter content. Read the ingredient list; look for “composted materials” as a component, not just mineral soil.
Skipping soil testing before adding amendments. Adding nutrients a soil already has is expensive and can create nutrient imbalances. Fertilizer applied over soil with excess phosphorus, for example, can actually suppress root development.