Topsoil vs Compost vs Garden Soil: What to Use and When

The question comes up constantly before any lawn or garden project: should I use topsoil, compost, or garden soil? They're sold next to each other at every hardware store and landscape yard, they look similar in a pile, and their descriptions overlap enough to cause genuine confusion. They're not interchangeable — using the wrong one for your project is one of the more common (and fixable) gardening mistakes.

This guide explains what each product actually is, when to use it, what it costs, and how to combine them for the most common projects.

Quick Reference

What Is Topsoil?

Topsoil is the upper layer of native soil — typically the top 2–8 inches of the ground profile. It contains a mix of mineral particles (sand, silt, and clay), organic matter from decomposed plant and animal material, and soil microorganisms. Good screened topsoil has a loose texture, dark color, and earthy smell.

The key word when buying topsoil is screened. Screened topsoil has been run through a mechanical screen to remove rocks, roots, and large debris. Unscreened topsoil may contain chunks, rocks, and inconsistent texture — fine for backfill behind a retaining wall, not fine for a new lawn or planting bed. Always ask specifically for screened topsoil for any project where plants need to grow.

What topsoil provides that compost doesn't: volume and mineral structure. If you need to raise a grade, fill a low spot, or create 4 inches of growing medium over a large area, topsoil is what you order. Compost is too expensive and too light to use at that scale.

For 2026 pricing by type (screened, premium, bulk vs. bagged), see the topsoil cost guide. To calculate how many cubic yards you need, see how much topsoil do I need or use the calculator below. You can also order screened topsoil online for delivery.

What Is Compost?

Compost is fully decomposed organic material — leaves, food scraps, grass clippings, and other plant matter that has broken down into a dark, crumbly, nutrient-rich substance. It looks like very dark, loose soil but has little mineral content. It's not a soil replacement; it's a soil amendment.

What compost provides that topsoil doesn't:

• Nutrients. Compost is high in nitrogen, phosphorus, potassium, and trace minerals — the raw ingredients for plant growth. It releases them slowly as microorganisms break it down further.
• Soil structure. In clay soils, compost opens up compaction and improves drainage. In sandy soils, it adds water retention. Both improvements happen because compost creates space for air and roots.
• Biological activity. Compost introduces and feeds beneficial bacteria, fungi, and earthworms — the living component of healthy soil that pure topsoil alone often lacks.

What compost doesn't provide: volume at a reasonable cost. A cubic yard of compost weighs much less than topsoil and costs more per yard. If you need to fill a 10×20 ft bed 6 inches deep, pure compost would cost $100–$200+ in material alone. The solution is to mix it into topsoil rather than use it by itself. You can order bulk compost online for delivery.

What Is Garden Blended Soil?

Garden blended soil (sometimes sold as "garden mix" or "planting mix") is a pre-combined product — typically screened topsoil blended with compost, and sometimes perlite or other amendments. It's a convenient middle ground: better than plain topsoil for planting, more affordable than buying and mixing topsoil and compost separately.

The trade-off is that you don't control the ratio. Blends vary by supplier — some are 70% topsoil with a light compost addition, others are closer to a 50/50 mix. For most in-ground garden beds, a good blend is a solid choice. For raised beds where you want a specific soil mix, buying components separately and blending yourself gives you more control (see the raised bed section below). A landscape yard or bulk supplier can quote garden blended soil by the yard — call ahead and ask about the topsoil-to-compost ratio so you know what you're getting.

What About Fill Dirt?

Fill dirt deserves a mention here because it gets confused with topsoil regularly — especially on new construction sites where both are present. Fill dirt is subsoil: it has little to no organic content, doesn't support plant growth, and is used for structural purposes only. It's what goes under the topsoil to raise a grade or fill a void.

If your project involves raising an area more than 4–6 inches, the economical approach is to fill with fill dirt to near-final grade, then cap with 4–6 inches of screened topsoil for the planting layer. Fill dirt is often free or very cheap; no reason to use expensive screened topsoil to fill a 12-inch void. See the fill dirt guide for more on this.

When to Use Topsoil

• New lawn installation — sod or seed both need at least 4 inches of workable topsoil. If your subgrade is clay or construction debris, you need topsoil before anything else goes down.
• Leveling and grading — filling low spots, correcting drainage toward the house, or creating positive grade away from a foundation.
• Large-volume fill — whenever you need more than a few inches of growing medium over a large area, topsoil is the only cost-effective option.
• Top-dressing bare soil before seeding — a 1–2 inch layer of screened topsoil over rough subgrade gives grass seed a much better germination environment than bare clay or fill.

When to Use Compost

• Amending existing soil — till 2–3 inches of compost into the top 6 inches of an existing planting bed before the season. This is the highest-impact annual garden task, and compost is what makes it work.
• Top-dressing an established lawn — apply ¼–½ inch of compost over grass in fall or early spring, then rake lightly to work it into the thatch layer. It feeds the soil biology and improves the lawn over 2–3 seasons without any tilling.
• Mixing into a new bed — any new in-ground planting bed benefits from 30–40% compost mixed into the topsoil layer.
• Side-dressing vegetables mid-season — a handful of compost worked into the soil around heavy feeders (tomatoes, squash, corn) in midsummer is the simplest mid-season fertilizer available.

Raised Bed Soil Mix: How to Blend Them

Raised beds are where topsoil, compost, and amendments work best together. Because the bed is contained and you're filling it from scratch, you control the mix completely. The standard blend for most vegetables and perennials:

• 60% screened topsoil — provides the mineral base and volume
• 30% compost — nutrition, soil structure, biological activity
• 10% perlite — improves drainage and prevents compaction over time

This 60/30/10 mix is sometimes called "Mel's Mix" (with vermiculite instead of perlite) and has a long track record in intensive vegetable gardening. It stays loose after multiple seasons, drains quickly, and needs only a compost top-dress each spring to stay productive — no tilling required in subsequent years.

Galvanized steel raised beds (use code YardCalc for 10% off) are a popular choice for this type of mix because they hold volume well at a depth that lets you run the full 60/30/10 blend without running short. The full raised bed build — soil depth, cardboard base layer, and frame sizing — is covered in the raised garden bed guide.

To calculate exactly how much of each component you need for your specific bed dimensions, use the raised bed calculator — it handles the volume math across multiple beds at once.

Compost Top-Dressing for Lawns: A Deeper Look

Top-dressing with compost is one of the best things you can do for an established lawn and one of the most underused techniques. The process:

1. Mow the lawn short (2 inches) before applying, so the compost reaches the soil surface rather than sitting on top of long grass.
2. Apply ¼–½ inch of compost across the lawn surface. A cubic yard covers roughly 650–1,300 sq ft at that depth. Use a shovel to toss it in small piles across the area, then rake level.
3. Water lightly to help the compost settle into the thatch layer.
4. Optionally overseed thin areas immediately after — the fresh compost is a good germination medium for grass seed.

One cubic yard of compost is enough to top-dress roughly 800–1,000 sq ft at a ¼-inch depth. Use the topsoil calculator (set depth to 0.25 inches) to estimate how much compost you need for your lawn area.

Making Your Own Compost

If you have the yard space and a consistent source of kitchen scraps and yard trimmings, a backyard compost bin pays back its cost in one season. A simple compost bin takes up about 3 sq ft of space, requires no electricity, and converts kitchen scraps and lawn clippings into usable compost in 3–6 months. The resulting compost is higher quality than most bagged products because it's made from your yard's own organic material and hasn't been dried and packaged.

The basics: alternate brown materials (dry leaves, cardboard, straw) with green materials (vegetable scraps, grass clippings, coffee grounds) in roughly equal proportions. Keep it moist but not soggy. Turn it every 2–3 weeks to aerate. Finished compost is dark, crumbly, and smells like earth — not decomposing material. It's ready when you can't identify any of the original inputs.

Home composting makes the most sense when you have a regular source of inputs and a use for 1–2 cubic yards of compost per year — a garden bed, annual lawn top-dressing, or raised beds to maintain. For larger projects (filling new beds, new lawn installation), you'll still need to supplement with bulk purchases.

Topsoil Calculator

Use this to estimate cubic yards and tons for your project. Works for topsoil, compost, or garden blend — the volume math is identical.

Soil Test: The Step Most People Skip

Before buying topsoil or compost, knowing what your existing soil is missing tells you how much amendment is actually needed. A basic soil pH test kit costs about $15 and tells you whether you need lime (to raise pH) or sulfur (to lower it) before you plant. Most vegetables and lawn grasses want pH between 6.0–7.0; adding compost to soil that's outside that range still won't fix the underlying problem.

County extension services often offer free or subsidized soil testing with a full nutrient analysis — worth a search for your county before spending money on amendments you might not need.

Related Guides

• Topsoil Cost Guide — bulk vs. bagged pricing, delivery costs, and what screened topsoil actually costs per yard in 2026
• How Much Topsoil Do I Need? — depth guide and quantity math for lawns, beds, and raised beds
• Raised Garden Bed Guide — full build guide including soil mix, frame sizing, and what to plant
• How Much Fill Dirt Do I Need? — for raising grade before topsoil and the compaction factor most people skip