Fill Dirt vs Topsoil: Differences, Uses and Tons to Order

Fill dirt vs topsoil comes down to one question: is the soil there to hold something up, or to grow something? Fill dirt is subsoil with little organic matter, so it packs down and stays put. Topsoil is the dark upper layer full of organic material, so it feeds roots but settles and shifts as it breaks down. Ordering the wrong one is a common reason for sunken patches, soft driveway edges and lawns that never take. This guide explains how the two differ, where each belongs, how to layer them on a grading job, and how to turn your area into cubic yards and tons.

Open the base calculator →

What fill dirt is

Fill dirt is the soil that sits below the topsoil layer. It is mostly mineral: sand, silt, clay and some stone, with very little leaf litter or root material. Because there is almost nothing in it to rot away, a properly compacted lift of fill keeps its volume over time. That is exactly what you want under a slab, a driveway, a patio or a regraded slope.

Yards sell it under several names. Clean fill usually means soil with no trash, concrete chunks, roots or large rocks. Select fill or structural fill usually points to a tested material with a known mix of sand and fines that compacts well, and engineers often call for it under buildings. Common fill or unscreened fill is whatever came out of a nearby dig, so quality can swing from load to load. Ask what is in the pile before it lands in your yard.

What topsoil is

Topsoil is the upper few inches of ground where most plant roots live. It is darker because it carries decayed organic matter, and it holds air and water in a way plants like. Suppliers commonly offer it screened (run through a mesh to pull out rocks, clods and roots) or unscreened. Some also sell blends with compost or sand mixed in for gardens and new lawns.

The same organic matter that makes topsoil good for grass makes it a poor structural layer. It compresses under load, holds moisture and slowly breaks down, so anything built on a thick bed of topsoil tends to settle unevenly.

Fill dirt vs topsoil at a glance

Job: fill dirt raises grade and supports weight; topsoil grows grass, plants and gardens.
Organic content: fill is low; topsoil is high.
Settling: compacted fill stays stable; topsoil keeps settling as organic matter breaks down.
Drainage: depends on the mix for fill (sandy fill drains, clay fill holds water); topsoil holds moisture for roots.
Price: fill is usually the cheaper of the two per yard, and screened topsoil usually costs more than unscreened. Local prices vary, so get quotes.
Where it goes: fill on the bottom, topsoil as the final few inches.

When to use fill dirt

Raising a low yard or filling a hole, old pool or trench before the finish layer goes on.
Building up grade around a house so the ground slopes away from the foundation.
Under a driveway, slab or patio where the ground needs to be built up before stone base goes down. Our topsoil under a new driveway guide explains why the organic layer should come out first.
Backfilling behind walls or around footings, where a plan or the wall maker may call for gravel instead of soil. See crushed stone for retaining wall backfill.

When to use topsoil

Seeding or sodding a new lawn on top of graded fill.
Garden beds and raised beds, often mixed with compost.
Top-dressing thin or patchy turf with a light layer.
Covering the edges of a new driveway or walkway so grass can grow up to the paving.

How to layer them on a grading job

On most yard and site work, the two materials work together rather than competing:

Strip the existing topsoil and sod from the work area and set it aside if it is decent.
Place fill in lifts of a few inches at a time and compact each lift. Thick dumps of loose dirt settle for months. The same idea applies to stone; see compacting a gravel base in lifts.
Shape the grade so water runs away from buildings and paved areas.
Finish with topsoil where grass or plants will grow, commonly a few inches deep for a lawn. Do not put topsoil under paving.

Clay-heavy fill drains slowly and can heave. If your site is mostly clay, read paving asphalt on clay soil before you plan a driveway on it.

How much fill dirt or topsoil you need

Both are sold by the cubic yard or by the ton. Start with volume:

Cubic yards = length (ft) × width (ft) × depth (in) ÷ 12 ÷ 27

For example, raising a 20 ft × 30 ft area by 6 inches is 20 × 30 × 0.5 = 300 cubic feet, or about 11.1 cubic yards. For compacted fill, add extra because loose soil shrinks when you pack it; many crews pad the order by roughly 15 to 25 percent and adjust after the first load. Topsoil that is only spread and raked needs a smaller cushion.

To convert yards to tons, use the weight your supplier quotes for its own material. As a planning starting point, dry loose topsoil or fill often lands near 1 ton per cubic yard, and damp or clay-heavy soil can run 1.2 to 1.5 tons or more. Our how much does a yard of dirt weigh guide breaks that down by soil type and moisture, and how much does a yard of topsoil cover shows coverage at common depths.

Digging out for a driveway or patio often leaves a pile of old soil and sod you do not want back. If you need somewhere to take it, Dumpmapper has a guide to where to dump dirt and sod.

Buying tips

Ask what is in the fill. Clean, select or common fill can mean different things at different yards.
Look at the pile for trash, broken concrete, roots and big rocks before you accept a load.
Ask whether topsoil is screened and whether it has been mixed with compost or sand.
Be careful with free fill. Soil from an unknown site can carry debris, invasive weeds or contamination.
Plan the drop spot on firm ground away from septic lids, soft lawn and overhead wires. For small moves, how many wheelbarrows in a yard helps you plan the labor.

Questions people ask

What is the difference between fill dirt and topsoil?

Fill dirt is low-organic subsoil used to raise grade and support weight because it compacts and stays put. Topsoil is the dark, organic upper layer used to grow grass and plants, and it settles over time.

Can I use topsoil instead of fill dirt?

Not under anything that has to stay level. Topsoil compresses and breaks down, so a driveway, slab or patio built on it tends to sink. Use fill for the build-up and keep topsoil for the final growing layer.

Can grass grow in fill dirt?

Grass struggles in plain fill because it has little organic matter. Spread a few inches of topsoil over graded fill before you seed or lay sod.

How much does a yard of fill dirt weigh?

As a planning number, dry loose fill often runs close to 1 ton per cubic yard, while damp or clay-heavy fill can run 1.2 to 1.5 tons or more. Use your supplier's figure for its own material when you order by the ton.

Is fill dirt cheaper than topsoil?

Usually, yes. Fill is typically the lower-cost material per yard, and screened topsoil usually costs more than unscreened. Prices vary by region and delivery distance, so get local quotes.

What is clean fill dirt?

Clean fill generally means soil without trash, concrete chunks, roots, large rocks or contamination. Yards define it differently, so ask what is in the pile and look at it before delivery.

As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.