Fill Dirt Calculator: How Much Fill Dirt Do You Need?

Fill Dirt vs. Topsoil: Which Do You Need?

Fill dirt is subsoil removed during excavation — it has little to no organic matter and is used purely for structural support, grading, and volume. It's appropriate for: - Filling depressions, sinkholes, and low spots - Raising grade around foundations - Backfilling utility trenches - Creating berms and mounds

Topsoil is the upper 4–12 inches of soil, rich in organic matter and nutrients. Use it as the final 4–6 inch layer over fill dirt when you want to grow grass or plants.

Most projects use fill dirt for the bulk volume and topsoil only for the top layer.

Fill Dirt Volume Formula

Volume (cubic yards) = Length (ft) × Width (ft) × Depth (ft) ÷ 27

One cubic yard = 27 cubic feet.

Example: You need to fill a 30 × 15 ft area to an average depth of 6 inches (0.5 ft): Volume = 30 × 15 × 0.5 ÷ 27 = 225 ÷ 27 = 8.3 cubic yards

For irregular areas, break the area into rectangles, calculate each separately, and sum them.

Compaction Factor

Fill dirt compacts 10–25% after settling and mechanical compaction. For structural applications (near foundations, under slabs), plan to apply material in 6–8 inch lifts and compact each lift before adding the next.

Compacted volume needed: Calculate the final volume you need, then multiply by 1.15–1.25 to determine the loose volume to order.

Example: Need 8 cubic yards of compacted fill → order 8 × 1.20 = 9.6 cubic yards (round up to 10 cubic yards).

Cubic Yards to Tons Conversion

Fill dirt weight depends on moisture content and soil type: - Dry sand or sandy loam: ~1.35 tons/cubic yard - Clay fill: ~1.5 tons/cubic yard - Average mixed fill: ~1.4–1.5 tons/cubic yard

For our 10-cubic-yard example: 10 × 1.45 = 14.5 tons

Most fill dirt is delivered by the truckload: - Small dump truck: 8–10 cubic yards - Standard tandem: 12–14 cubic yards - Large tri-axle: 18–22 cubic yards

Fill Dirt Cost Estimate

Fill dirt is typically the cheapest material for grading:

Many homeowners source fill dirt for free or near-free from local excavation contractors who need to dispose of it. Sites like dirtmatchup.com or Craigslist often list free fill dirt offers.

Grading Around a Foundation: Special Considerations

Building codes require positive drainage away from foundations: - Grade should slope at least 6 inches over the first 10 feet away from the foundation - Never place fill dirt against wood framing without proper waterproofing - Allow 6 inches between fill dirt and any wood sill plate or framing

Improperly placed fill that redirects water toward the foundation causes more damage than it prevents.