🚜 Earthmoving & Grading Estimator

Fill Dirt Calculator

Calculate exact cubic yards, compaction shrinkage factors, dump truck haul quantities, and total material costs for foundation backfill, trenching, and ground grading.

Civil Earthwork & Subgrade

Fill Dirt Calculator

Calculate cubic yards, tons, and truckloads for grading pads, trench backfills, sinkholes, and slopes.

Flat Area / Yard DimensionsFeet & Inches

1. Estimated Volume Loss During Compaction (Shrinkage Rate)Formula: Loose = In-Place ÷ (1 - Loss Rate)

Loose delivered dirt compresses and loses void volume when compacted with plate compactors, rollers, rammers, or natural rainfall settling. Actual shrinkage depends on soil composition, moisture level, placement method, lift thickness, compaction equipment, and engineering specifications. Presets below represent common planning assumptions (e.g., at 15% estimated volume loss, a 100 yd³ in-place void requires 100 ÷ 0.85 = 117.65 yd³ of loose delivered dirt).

2. Optional Ordering / Spillage Waste BufferFormula: Total = Loose × (1 + Buffer)

Additional linear safety margin for uneven grade sub-base, grading run-off, or supplier volume variations.

Typical: 1.15 tons/yd³ (~2,300 lbs) for dry fill; 1.35 for wet clay.
Bulk pit average: $12 to $25 / yard before delivery.
Total Loose Fill Dirt Required15% Volume Loss Rate
8.71cu. yds.
235.29 cu. ft.6.66 m³~10.02 Tons
Final In-Place Void Volume:7.41 cu yd (200 cu ft)
Loose Dirt Required (15% Volume Loss):8.71 cu yd (235.29 cu ft)

Hauling & Delivery LogisticsTonnage-based estimates

1
Tri-Axle (10 yd)
Commercial Haul
2
Single-Axle (5 yd)
Residential Truck
~12
Pickup Loads
~1,700 lb payload
Total Delivered Weight:~20,044 lbs (10.02 US tons)

Estimated Material Cost

Material (8.71 yds @ $18/yd):$156.86
Estimated Delivery Fee:$75.00
Total Project Budget:$231.86

How to Calculate Fill Dirt for Common Excavation Shapes

1. Flat Yard & Pad Filling

Cubic Yards = (Length ft × Width ft × Depth in) ÷ 324

The contractor constant 324 combines 27 cu ft/yd³ with 12 in/ft. A 20×20 ft area at 6 inches deep requires (20 × 20 × 6) ÷ 324 = 7.41 cubic yards nominal.

2. Utility Trench & Foundation Backfill

Cubic Yards = Length ft × (Width in ÷ 12) × (Depth in ÷ 12) ÷ 27

For continuous utility or footing trenches, convert width and depth from inches into feet before multiplying by total linear run.

3. Depressions, Stump Holes & Sonotubes

Cylinder Yards = (π × (Diameter ft ÷ 2)² × (Depth in ÷ 12)) ÷ 27

For cylindrical holes, calculate circular area using the radius squared multiplied by pi, then apply depth.

4. Slopes & Tapering Grading Wedges

Average Depth = (Start Depth in + End Depth in) ÷ 2

Modeled geometrically as a right-triangular prism or trapezoidal wedge. Multiply footprint by the average vertical depth.

The Engineering Reality of Dirt Compaction & Settling

One of the costliest estimating errors on grading projects is failing to distinguish between bank volume (undisturbed earth in the ground), loose volume (fluffed earth loaded into a dump truck), and compacted volume (mechanically rolled earth in final placement).

⚠️ Compaction Rule of Thumb for Contractors:

When excavated subsoil is dropped loose from a dump truck chute, it contains 15% to 25% void air space. When compacted into a trench or building pad in 6-inch lifts using a vibrating plate or pneumatic tamper, that air is eliminated. Always add 10% to 15% extra volume (or up to 20% for deep foundation trenches) to ensure your finished grade does not sink below elevation lines after the first major freeze-thaw or rain cycle.

Fill Dirt vs. Topsoil: When to Use Each Material

Choosing between topsoil and fill dirt is determined strictly by the depth of application and structural intent:

Fill Dirt (Inorganic Subsoil)
  • Mined from beneath the organic biological soil horizon.
  • Contains clay, sand, and fine mineral aggregate with near-zero organic matter.
  • Does not decompose or create subterranean voids; compacts solid.
  • Best for: Raising land grade, backfilling foundation walls, filling deep holes (> 6 inches), road subbase.
Topsoil (Organic Root Zone)
  • Top 2 to 8 inches of natural soil containing humus, minerals, and microbial life.
  • High moisture retention and fertile aeration properties.
  • Decomposes and shrinks if buried deeply; unsuitable for structural loads.
  • Best for: Top 4 to 6 inches of lawn turf, vegetable gardens, and tree root zones.
For a full cost, engineering, and plant health comparison, consult our guide: Fill Dirt vs Topsoil: Complete Usage & Cost Guide.

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Frequently Asked Questions

How many cubic yards of fill dirt do I need?

To find the in-place compacted volume for a flat area: multiply Length (ft) × Width (ft) × Depth (in) ÷ 324. In civil earthwork, loose delivered soil compresses when compacted; calculate loose material required as: Loose Volume = Compacted Volume ÷ (1 - Compaction Rate). For example, a 100 cu yd void at 15% compaction requires 100 ÷ 0.85 = 117.65 cu yd of loose delivered fill dirt.

How much does 1 cubic yard of fill dirt weigh?

One cubic yard of dry fill dirt typically weighs between 2,000 and 2,400 lbs (approx. 1.0 to 1.2 tons). Wet or compacted clay fill dirt can weigh 2,600 to 3,000 lbs (1.3 to 1.5 tons) per cubic yard.

How many yards of fill dirt fit in a dump truck?

A standard commercial tri-axle dump truck carries 10 to 14 cubic yards (approximately 14 to 18 tons), while a smaller single-axle residential dump truck carries 5 to 6 cubic yards. A standard half-ton pickup truck bed can carry approximately 0.5 to 0.75 cubic yards due to payload weight limits (1,500–2,000 lbs).

Can I use topsoil as fill dirt?

No. Topsoil contains high concentrations of decomposing organic matter (humus), which decomposes, shrinks, and creates underground voids over time. For deep structural backfilling, grading around building foundations, or raising low terrain, inorganic subsoil (fill dirt) is required to ensure long-term stability and prevent catastrophic settling.

How much does fill dirt cost per cubic yard?

In bulk from local quarries or dirt pits, raw fill dirt typically costs $8 to $20 per cubic yard before delivery fees. Delivery charges usually range from $50 to $120 per dump truck load depending on transit distance.

How do you calculate fill dirt for a sloped area?

To calculate fill dirt for a uniform slope or wedge: multiply Length (ft) × Width (ft) × Average Depth (ft). Average depth is calculated as (Starting Depth + Ending Depth) ÷ 2. For example, a 30 ft × 10 ft slope tapering from 0 to 12 inches has an average depth of 6 inches (0.5 ft), requiring (30 × 10 × 0.5) ÷ 27 = 5.56 cubic yards before compaction.