Fill Dirt vs Topsoil: Which One Do You Need?
Fill dirt goes under your lawn; topsoil grows it. You usually need both for a landscaping project. Learn how to calculate, price, and order the right material.
The short answer
Fill dirt is subsoil, ideal for filling holes and raising grade because it compacts well and doesn’t contain organic material that decomposes. Topsoil is the nutrient-rich top layer, used for planting grass, gardens, and flower beds. Choose fill dirt for structure; topsoil for growing.
Key takeaways
- Fill dirt packs tight: it's for filling and grading, not planting.
- Topsoil feeds plants: it has organic matter and nutrients for growth.
- Get your depths right: 6 inches of topsoil for lawns; 12+ inches of fill for low spots.
- Always over-order: add 10–15% for compaction and settling.
Whether you're fixing a bumpy lawn, building a garden bed, or leveling a construction site, knowing the difference between fill dirt and topsoil saves you money and dead plants. This guide breaks down what each material does, how to calculate how much you need, and what it'll cost.
What’s the difference between fill dirt and topsoil?
Fill dirt is the subsoil layer found beneath the topsoil. It's mostly clay, sand, and rock with no organic matter. Topsoil is the top 2 to 8 inches of earth, rich in decomposed plants and nutrients.
- Fill dirt is dense and stable; it compacts firmly and resists settling.
- Topsoil is loose and crumbly; it holds water and feeds roots.
- Use fill dirt to raise low spots, backfill foundations, or build up a base layer.
- Use topsoil for lawns, flower beds, and vegetable gardens, anything that grows.
- A typical project uses fill dirt below and topsoil on top. Check our topsoil and fill dirt calculator to estimate both.
How much fill dirt or topsoil do I need?
Calculate cubic yards by multiplying length × width × depth (in feet), then divide by 27. Depth is key: fill dirt is often needed in thicker layers than topsoil.
- Measure the area in square feet (length × width).
- Decide on your depth in feet (e.g., 6 inches = 0.5 feet).
- Multiply: square feet × depth = cubic feet. Divide by 27 to get cubic yards.
- For fill dirt, plan for compaction: order 10–15% extra.
- For topsoil, a 6-inch layer is standard for new lawns; use our topsoil and fill dirt calculator to do the math.
How much does fill dirt and topsoil cost?
Prices vary by region, but fill dirt is always cheaper than topsoil. Delivery fees can add $50 to $100 per load, as of early 2025.
- Fill dirt: $10 to $30 per cubic yard, depending on your location and supplier.
- Topsoil: $20 to $60 per cubic yard; screened topsoil costs more.
- Bulk delivery is cheaper per yard than bagged soil. Use our topsoil and fill dirt calculator to see if bulk makes sense.
- Some suppliers charge a minimum load fee, so ask before ordering.
- Extra delivery fees apply for small loads or long distances.
What are common mistakes when using fill dirt or topsoil?
Ordering the wrong material or the wrong amount is the biggest mistake. Both fill dirt and topsoil have specific jobs. Mixing them up can kill plants or cause settling.
- Mistaking fill dirt for topsoil when planting: fill dirt has no nutrients and will starve plants.
- Not ordering enough for compaction: fill dirt can settle up to 15%, so add extra.
- Using topsoil as fill: it decomposes over time, creating sinkholes.
- Skipping soil testing for topsoil: cheap topsoil may be full of weed seeds or rocks.
- Ignoring drainage: fill dirt can trap water if not graded properly; use our gravel calculator for drainage layers.
Can I mix fill dirt and topsoil?
You don't mix them together; you layer them. Fill dirt goes on the bottom for bulk and stability, and topsoil goes on top for planting.
- Put down fill dirt first to raise the grade or fill holes.
- Compact the fill with a tamper or plate compactor to prevent future sinking.
- Layer 4 to 6 inches of topsoil over the compacted fill for grass or plants.
- For garden beds, use all topsoil, no fill dirt, at least 12 inches deep.
- Check with a local pro if you're unsure about soil layering; visit our sand calculator if you need a sand base for pavers.
Should I install fill dirt or topsoil myself, or hire a pro?
Spreading a few yards of topsoil by hand is doable for a DIYer. Moving 10+ yards of fill dirt often requires a skid steer or pro.
- DIY: small projects like flower beds or patching are manageable with a shovel and wheelbarrow.
- DIY: order bulk delivery and have the truck dump where you need it; use our topsoil and fill dirt calculator to order the right amount.
- Hire a pro: for large grading jobs, poor access, or if you need machine compaction.
- Pros bring the right equipment to spread and level in hours, not days.
- Always get at least 3 quotes and ask for references if you hire out.
| Row | Fill Dirt | Topsoil |
|---|---|---|
| Uses | Filling holes, grading, backfilling | Planting grass, gardens, flower beds |
| Organic Matter | None or very little | 2–10% organic matter |
| Compaction | Compacts well, resists settling | Stays loose, may settle over time |
| Cost per Cubic Yard (as of early 2025) | $10–$30 | $20–$60 |
| Best for | Structure and stability | Plant growth |
Questions this page answers
What is fill dirt?
Fill dirt is the subsoil taken from below the topsoil layer. It contains clay, sand, and rock with very little organic material. It's used to fill holes, raise low spots, and create a stable base for construction or landscaping.
What is topsoil?
Topsoil is the upper 2 to 8 inches of earth. It's rich in decomposed organic matter and nutrients, making it ideal for growing grass, plants, and vegetables. Quality topsoil should be dark, crumbly, and free of weed seeds or debris.
Can I use fill dirt for a vegetable garden?
No. Fill dirt lacks nutrients and organic matter, so vegetables will struggle to grow. Always use topsoil or a quality garden soil mix for planting edible crops.
How do I calculate cubic yards for dirt?
Multiply the length by width by depth (all in feet) to get cubic feet. Then divide by 27 to convert to cubic yards. For example, a 10 ft × 10 ft area at 0.5 ft deep equals 50 cubic feet, or about 1.85 cubic yards.
Does fill dirt compact?
Yes. Fill dirt will compact and settle over time, especially after rain or when compacted with equipment. Always order 10–15% extra to account for this, and compact it in layers if you need a firm base.
How much topsoil over fill dirt?
Spread 4 to 6 inches of topsoil over a compacted fill dirt base for lawns and most plantings. For garden beds, skip the fill dirt entirely and use 12 inches or more of topsoil.
Can I put topsoil over clay?
Yes. You can layer topsoil over clay subsoil, but you may need more topsoil depth and should improve drainage by tilling or adding organic matter. A 6-inch layer is usually sufficient for a lawn.
Do I need to remove old grass before adding topsoil?
You can smother existing grass with a thick layer of topsoil, but the best practice is to remove old sod or kill the grass first. This prevents the old grass from growing through and creates a smoother finish.
Fill dirt and topsoil serve opposite but complementary purposes. Fill dirt provides the stable base; topsoil makes things grow. For almost every project, you'll need both. Get your depths right, order 10–15% extra for compaction, and use our topsoil and fill dirt calculator to nail the quantities and costs before you order.