Fill Dirt Calculator: How Much You Need
Use fill dirt calculator math: area in ft² × average depth in ft ÷ 27 = cubic yards, then add 10%–20% for compaction and waste before ordering. If you skip that buffer, low spots stay low, backfill settles, and pads come in short. We show the formula, a worked example, compaction allowances, and a quick sanity-check table for yards, tons, and truck loads.
What fill dirt is used for
Fill dirt is subsoil with little or no organic matter. It fills holes, levels low spots, builds pads, supports grading, and backfills around structures. It is a structural material, not a planting material, so we choose it for shape and stability rather than nutrients.
Fill dirt vs topsoil
Fill dirt and topsoil are not interchangeable. Fill dirt goes where settlement control matters, while topsoil is the better choice for planting because it contains organic material. Topsoil can settle more and is not the right base for patios, pads, or other load-bearing work.
Common jobs that need fill dirt
Most fill dirt orders fall into a few job types: patio base leveling, trench backfill, yard low-spot fill, slope building, and general grading. Each one needs a different depth method and a different compaction buffer, which is why one percentage does not fit every project.
Fill dirt density on Gravelshop is listed as 2,410 lb/yd³, or 1.21 t/yd³.
How do I calculate how much fill dirt I need?
Measure length and width, then take several depth readings and use the average depth in feet. Multiply length × width × average depth to get cubic feet, then divide by 27 to convert to cubic yards. On uneven ground, average depth gives a tighter order than the deepest point.
Basic formula
The core formula is simple: length × width × depth = cubic feet, then cubic feet ÷ 27 = cubic yards. One cubic yard equals 27 cubic feet, so this conversion is required whenever the supplier sells by the yard.
Worked example
For a 24 ft by 18 ft area at about 0.5 ft average depth, the volume is about 216 cubic feet. Dividing by 27 gives about 8 cubic yards. If the job needs a buffer of around 15%, order a little over 9 cubic yards and round up to 10.
How to measure depth correctly
- Measure the length and width of the fill area in feet.
- Take several depth readings, especially where the surface is uneven.
- Use the average depth for the whole section if the area is irregular.
- Convert cubic feet to cubic yards by dividing by 27.
- Add the job-specific compaction allowance before placing the order.
How much extra fill dirt should I order for compaction?
Most fill dirt orders need extra material for settling, tamping, and moisture loss. A practical allowance is often in the rough range of 10% to 30%, and many backfill and leveling jobs seem to land around 15% to 20%. The right buffer depends on the soil, the lift thickness, and how much compaction the job requires.
Choosing a compaction allowance
A light leveling job may need only a small buffer, while trench backfill or a pad built in lifts may need more. FigureCalc recommends 15% for many backfill and leveling projects, while general guides often cite 10% to 20% for settling. Deep fills or wet, loose soil can justify more.
Simple ordering rule
Use 10% to 15% for light leveling with good subgrade conditions, 15% to 20% for most backfill and general grading, and 20% to 30% for deep fill, sloped areas, or soil that will be compacted in layers. That rule keeps the order tied to the job, not a fixed default.
How do I estimate fill dirt for a slope or uneven area?
For slopes and uneven ground, average depth is usually better than the deepest point because the whole area is not filled to the maximum depth. Break the site into smaller rectangles, triangles, or wedges, estimate each section separately, and then add the volumes together.
When average depth beats deepest depth
Use average depth when the ground rises and falls across the area, or when one side of a section is much deeper than the other. Measure the shallow side, the deep side, and one or two points in between, then calculate a realistic middle value rather than assuming the maximum applies everywhere.
Wedge and low-spot example
If a 20 ft by 10 ft strip tapers from about 0.25 ft to 1.25 ft, the average depth is about 0.75 ft. The volume works out to about 150 cubic feet, or roughly 5.6 cubic yards. With a 20% buffer, the order rises to 6.7 cubic yards, so 7 yards is the practical buy.
Irregular shapes and divided areas
Infinity Calculator accepts rectangles, circles, triangles, acreage, and square footage. That matters because many fill jobs are not one clean rectangle. Circles, triangles, and stepped areas should be split into smaller parts, measured separately, and combined so the final order reflects the actual fill shape.
Fill dirt estimate by job type
Job type changes the depth method and the compaction buffer. Use average depth for uneven areas, deepest depth only for a contained hole with near-vertical sides, and a larger buffer when the material will be compacted hard or placed in a slope. The table below gives a practical ordering range.
| Job type | Typical depth method | Compaction buffer | Order quantity range | When to use average depth |
|---|---|---|---|---|
| Patio base leveling | Average depth | 10% to 15% | 4 to 6 inches of fill over the area, then add buffer | Use average depth if the base has dips or a slight crown |
| Trench backfill | Measured trench depth | 15% to 20% | 1 to 3 cubic yards for short runs; more for long utility trenches | Use average depth if trench depth changes along the run |
| Yard low-spot fill | Average depth | 10% to 20% | Small patches often order 1 to 5 cubic yards | Use average depth whenever the low spot is bowl-shaped |
| Slope fill | Average depth across the wedge | 20% to 30% | Often 5 to 15 cubic yards or more, depending on runout | Use average depth unless the fill is a uniform retaining fill |
One-line rule: measure deepest depth only for a contained hole; use average depth for anything that changes depth across the area, including slopes, bowls, and mixed sections.
How many tons or truckloads of fill dirt do I need?
To estimate tons, multiply cubic yards by density, but note that density changes with soil type and moisture. Fill dirt density on Gravelshop is listed as 2,410 lb/yd³, or 1.21 t/yd³, and FigureCalc says typical fill dirt runs 1.0 to 1.3 tons per cubic yard.
Convert cubic yards to tons
Using that conversion factor, a 10-yard order weighs about 12 tons. If the supplier’s material is wetter, looser, or more granular, the tonnage can shift. That is why tonnage should be treated as an estimate, not a fixed constant.
Truckload estimation
Truck capacity varies by dump truck size, so cubic yards are best translated into loads only after the supplier’s truck rating is known. A small load may fit in one trip, while larger orders may need multiple deliveries. Use the yard total first, then ask the supplier how their truck size maps to that volume.
When tonnage matters more than volume
Volume is usually the ordering unit, but tons matter when the supplier quotes by weight or the receiving site has weight limits. For mixed deliveries or tight access, having both figures helps with scheduling and avoids surprises when the load arrives wetter or denser than expected.
Fill dirt calculator assumptions and sanity checks
Our calculator estimates soil, topsoil, or fill dirt needed by length, width, and depth. It also shows material weight in dry, loose, packed, compacted, and wet forms. The arithmetic uses the same unit discipline every time: measure in feet, compute cubic feet, then divide by 27 for cubic yards.
Square feet covered per cubic yard
One cubic yard covers different square footage depending on depth. This quick check helps catch underordering before a load is placed.
| Depth | Square feet covered by 1 cubic yard | Use it for |
|---|---|---|
| 2 in | 162 sq ft | Very shallow leveling |
| 4 in | 81 sq ft | Light grade correction |
| 6 in | 54 sq ft | Common fill and leveling depth |
| 12 in | 27 sq ft | Deep fill or pad build-up |
Sanity checks before ordering
If a large area at 6 in depth produces less than expected, recheck whether the depth was entered in inches instead of feet. If a slope was measured with deepest depth only, the order is usually too large. If a backfill job ignores settling, the order is often too small.
Frequently asked questions
how to calculate how much fill dirt i need
Measure length, width, and average depth in feet, multiply them to get cubic feet, and divide by 27 to convert to cubic yards. Then add a job-specific buffer for compaction and waste. Average depth matters most on uneven ground, where deepest-point math usually overshoots the order.
how much fill dirt do i need calculator
A fill dirt calculator uses the same volume math as a manual estimate: area in ft² times average depth in ft, divided by 27. Better tools also let you account for compaction and may show the material weight in dry, loose, compacted, and wet forms.
how much fill dirt do i need
The amount depends on the area, the depth, and the job type. A shallow leveling job may need only a few yards, while slope fill or deep backfill can need much more. The most reliable estimate comes from average depth, not from a single deepest reading.
how to calculate dirt fill
Use length × width × depth for rectangular sections, or split irregular shapes into smaller parts and calculate each one separately. Convert cubic feet to cubic yards by dividing by 27, then add extra for compaction, settling, and waste before placing the order.
how to calculate fill dirt with compaction
First calculate the loose volume in cubic yards. Then add a compaction allowance, usually 10% to 30% depending on the job. Light leveling can use the low end, while trench backfill, slope fill, and heavily compacted pads usually need more than a minimal buffer.
how many cubic yards of fill dirt do i need
Multiply the area by the average depth in feet, then divide by 27. For example, 30 ft × 20 ft × 0.5 ft equals 300 cubic feet, or 11.1 cubic yards. After adding compaction, the order becomes about 13 yards if a 20% buffer is used.