Fill Dirt Calculator — Georgia

Fill dirt is subsoil dug from below the topsoil layer. It carries little or no organic matter, which is the trait that defines it. You use fill dirt to build volume and hold a shape under a load, not to grow anything. This calculator sizes a fill dirt order by volume, reporting the cubic yards and the tons you need from the area and the finished depth you enter.

Topsoil is the opposite material for the opposite job. It is the dark upper layer rich in roots, decayed plants, and living matter, and it exists to feed what grows in it. Fill dirt sits below that layer, where the color lightens to clay, sand, or rocky subsoil. The two look different in the pile and behave in opposite ways once you place them.

The organic content is why the two are not interchangeable. Organic matter rots and breaks down over time, and as it does it leaves voids. A fill built from organic-rich soil keeps settling for years as the plant matter decays. Subsoil has nothing left to rot, so once you compact it, it stays put. That stability is the whole point of fill dirt.

This is why a builder strips the topsoil off a site before any structural work and stockpiles it to one side. The good growing soil is saved for the finish grade and the beds. The structural volume underneath gets clean subsoil fill that will not decay under a slab or a pad. Keep the two as separate orders for separate jobs.

Do not order fill dirt for a lawn you plan to seed or a bed you plan to plant. Little grows in subsoil, because the nutrients and the structure roots need are not there. If your project needs both a raised, stable base and a growing surface, order fill dirt for the base and topsoil for the top few inches.

Fill dirt sells in grades, and the grade you need depends on the load the fill will carry. The volume is the same either way, so the calculator sizes any grade from the same area and depth. The grade is a quality choice, not a quantity one, but ordering the wrong grade can stall or fail the job.

Clean fill is subsoil screened free of debris. It carries no trash, no large rocks, no roots, and no construction waste. It suits jobs where the fill raises a grade or fills a void but does not sit under a structure. Raising a low spot in a yard, filling an old pool or a stump hole, and backfilling a trench are clean-fill jobs.

Structural fill, sometimes called engineered fill, is a step up. It is a specified material that compacts to a known density and carries a designed load. You place it under a building pad, a slab, a driveway, or against a foundation, anywhere the fill becomes part of the structure. On those jobs an engineer or the local code often sets the material and the compaction standard.

Match the grade to the use before you order. A grade raise or a backfill against a simple wall takes clean fill. A pad that will carry a slab or a drive takes structural fill, placed and tested to the spec. Using clean, unspecified fill under a structure risks uneven settling and a cracked slab later.

Name the grade when you call the yard. Ask for clean fill if you want debris-free subsoil for grading. Ask for structural or engineered fill, by the spec, if the job is load-bearing. Confirm the material is free of trash and large rock before the truck loads, because sorting debris out of a dumped pile is slow, costly work.

Fill dirt arrives loose and full of air. The moment you place it and compact it, the soil packs together and the surface drops below the loose depth you spread. This settling is the single trait that catches people out on a fill job, and planning for it is the difference between a grade that holds and one that sinks.

The lesson is simple: order more loose material than the finished volume. If you measure the hole or the grade raise and order exactly that volume, you will run short once the fill compacts. The loose pile on the truck shrinks as it packs down into the finished layer. Buy for the loose amount it takes to reach your finished depth after compaction.

This calculator builds in a compaction and settlement allowance, set to 10 percent by default. It sizes the finished volume from your area and depth, then adds that allowance so the loose fill you buy packs down to the grade you planned. Keep the allowance on. It also covers the fill lost into an uneven subgrade and spilled at the edges.

Deep fills settle more than shallow ones, because there is more loose material to pack down. On a deep hole, an old pool, or a tall grade raise, raise the allowance above the default. A thick fill placed in one dump settles the most of all, because the lower part never reaches density under its own weight.

Fill that is dumped and left uncompacted keeps settling on its own for months. Rain speeds it up, as water washes the fines into the voids and the surface drops. A raised grade that looked right in the spring can dish by the next year if the fill was never packed. Compacting now, in lifts, is what stops a sunken grade later.

Depth sets the order more than any other input, and the right depth follows the job. Fix the finished depth of fill before you read the totals, because the calculator sizes everything from that number.

A grade raise spreads a shallow layer over a wide area. Measure the drop you want to correct, from the low point up to the grade around it. A spot that pools water after rain often needs a few inches of fill to bring it level. Spread it evenly and check the grade across the whole area, not just at the edges.

A backfill follows the shape of the excavation. Measure the width, length, and depth of the space the fill must fill, whether it is a trench, a void against a foundation, or a formed area. An uneven trench is hard to judge from one reading, so take several depths along it and use the average.

A hole or an old pool is a volume job, not a layer job. Measure the depth at the deepest point and estimate the average across the opening, since the bottom is rarely flat. These deep fills use a lot of material, so measure with care and lean on the allowance.

A building pad must sit above the surrounding grade so water runs off it. Set the finished height of the pad first, then measure down to the existing ground to find the fill depth. Break any odd footprint into simple rectangles, size each part on its own, and add them. If the depth changes across the site, run the calculator for each zone and sum the results before you order.

The amount the calculator gives you assumes the fill sits on firm, prepared ground and goes down in compacted layers. Loose or dirty ground under the fill, or a single thick dump, undoes the work no matter how well you measured.

Prepare the subgrade first. Strip the sod, roots, and topsoil from the area, because that organic ground rots and settles and leaves voids beneath your fill. Then compact the exposed subsoil until it holds firm. A loose subgrade sinks under the weight of the fill above it and takes your finished grade down with it.

Place the fill in lifts, not all at once. Spread several inches, compact that layer, then add the next. These compaction lifts drive the density all the way to the bottom. A thick single dump packs only at the top and leaves a loose zone below that settles later and dishes the surface.

Moisture controls how well fill packs. Soil that is too dry will not lock together, and soil that is too wet turns to mud and will not hold density. Damp fill, close to the right moisture, compacts best. Water a dry lift lightly before you pack it, and let a soaked site dry before you work it.

Grade the surface to drain as you build. A finished grade or a pad should slope away from any structure so water runs off instead of pooling against a wall or soaking into the fill. Build that slope into the top lift. Water that stands on or in a fill softens it and drives the settling you worked to prevent. Check the finished level at many points, because a low spot in the middle means the fill is not even.

Fill dirt sells by the cubic yard or by the ton, so the calculator reports both. A cubic yard is a block three feet on every side, which equals 27 cubic feet of volume. A ton is a measure of weight. The density of the soil ties the two together.

Fill dirt runs about 1.25 tons per cubic yard as a planning figure, within a range of 1.2 to 1.4. The value shifts with the soil type and its moisture. Clay-heavy fill packs dense and weighs more. Sandy fill weighs less. Wet soil weighs more than dry soil of the same kind. Ask your supplier for the weight of the fill they carry if you buy by the ton.

The tool handles the conversion. It sizes the cubic yards from your area and depth, adds the settlement allowance, then multiplies by the density to reach tons. If you hold one number and need the other, multiply cubic yards by about 1.25 for tons, or divide tons by 1.25 for yards.

Report both because suppliers differ. Many landscape yards sell bulk soil by the cubic yard, which matches a volume estimate. Pits weigh the loaded truck on a scale, so the delivery ticket lists tons. Having both lets you match the yard and check your order against the weight slip when the truck arrives.

Bulk fill dirt comes by dump truck, and one truck holds roughly 10 to 14 cubic yards. Divide your total by that range to see the loads. A small grade raise fits in part of one load, while a deep hole or a large pad can run past a single truck. Name the grade when you order, pick a drop spot close to the work but clear of the excavation, and lay a tarp under the pile to keep the fine soil off a lawn and out of the rain.

Most fill problems trace to a short list of errors, and the worst of them show up months later as a sunken grade. Knowing them ahead saves a second delivery and a failed pad.

The first is entering depth in the wrong units. The tool wants inches. Type feet where inches belong and the estimate swings far off. Read the depth back before you trust the total, so a 6 means six inches, not six feet.

The second is ignoring settlement. Loose fill packs down once compacted, so an order sized for the finished volume comes up short. Order for the loose amount needed to reach the finished depth, and keep the compaction allowance on to cover it.

The third is ordering fill dirt where the job needs topsoil, or the reverse. Fill dirt builds structural volume and will not grow plants. Topsoil grows plants and will not hold a stable load. Ordering the wrong one wastes the load and stalls the work.

The fourth is dumping the full depth in one thick layer and skipping the lifts. The bottom never reaches density, so the fill settles later and the grade dishes. Place and compact in layers of several inches. The fifth is measuring a rough hole as a clean box, when a pit or an old pool varies in depth and shape. Take several readings, use the average, and break odd shapes into simple parts.

The last is ordering exactly the estimate with no margin on a load-bearing or deep fill. Ground is uneven, fill settles, and spills happen. Keep the allowance on, round up to the next practical amount, and lean toward structural fill when the load is real. A small surplus is far cheaper than a sunken grade and the repair it forces.