Fill Dirt Calculator
Enter your area dimensions, pick a soil type and truck size, and get an instant cubic yard count with tons and truckloads.
To calculate how much fill dirt you need, multiply the length of your area (in feet) by the width (in feet) by the depth (in feet), then divide by 27 to convert to cubic yards. Add a 10–20% compaction buffer — a 15% buffer is appropriate for most residential projects.
- Expert Reviewed
- Updated May 2026
- Sources Cited
- No Login Required
- Free to Use
Formula: Length × Width × Depth ÷ 27 = base cubic yards. Compaction buffer added on top. Weight conversion uses ASTM D698 dry density ranges for the selected soil type.
Compaction Buffer
Adjustable 0–30% slider. 15% default for residential; 20–25% for clay or structural fill.
5 Soil Densities
Sandy to clay-heavy — each with its own tons-per-cubic-yard conversion from ASTM D698 ranges.
Engineer-Reviewed
Compaction rationale, ASTM D698 citations, and structural fill guidance reviewed by Alex Rivera, PE.
Formula based on ASTM D698 dry density ranges. Compaction factor reviewed by Alex Rivera, PE (CA #C-89412).
How Much Fill Dirt Do You Need? (Quick Answer)
Multiply length × width × depth (all in feet), then divide by 27 to get cubic yards. Always add a compaction buffer — 15% is the reliable default for most residential projects. For a 20 × 15-foot area at 6 inches deep: 20 × 15 × 0.5 ÷ 27 = 5.56 cubic yards base volume; with 15% compaction buffer, order 6.4 cubic yards.
Fill Dirt Formula (How the Calculator Works)
The fill dirt formula is: Volume (cu yd) = L (ft) × W (ft) × D (ft) ÷ 27. Depth in inches must be divided by 12 before multiplying. The number 27 converts cubic feet to cubic yards — one cubic yard is 3 ft × 3 ft × 3 ft = 27 cubic feet.
Worked Example: 10 ft × 10 ft at 6 Inches
Why Add a Compaction Buffer?
Loose fill dirt shrinks when it is spread and tamped. A truck delivers cubic yards of fluffed material; once a vibratory plate passes over it, the same dirt occupies a smaller volume. Order only the base calculation and your fill will finish below grade.
"The right compaction buffer depends on your soil type and project requirements. Granular and sandy fill typically compacts 10–12%. Clay-heavy fill can shrink 20–25% from loose volume. For structural applications — foundations, retaining walls, road bases — ASTM D698 (the Standard Proctor test) sets the target density. Most residential structural specs call for 95% of maximum dry density at optimum moisture content. For general yard leveling, 15% is a reliable conservative default."
Convert Cubic Yards to Tons
One cubic yard of fill dirt weighs roughly 1.35 to 1.82 short tons depending on soil classification. For mixed or unscreened residential fill, use 1.55 tons per cubic yard as your working estimate. The calculator converts automatically when you select a soil type.
Fill Dirt Weight by Soil Type
| Soil Classification | Dry Unit Weight (lb/ft³) | Approx. Tons / cu yd | Notes |
|---|---|---|---|
| Sandy Fill / Granular | 100–115 | 1.35–1.55 | Best draining; common structural fill base |
| Sandy Loam | 115–125 | 1.55–1.69 | Good general fill; moderate compaction |
| Silty Fill | 110–120 | 1.49–1.62 | Moderate plasticity; moisture-sensitive |
| Clay-Heavy Fill | 120–135 | 1.62–1.82 | High compaction shrinkage; settles most |
| Mixed / Unscreened | 110–125 | 1.49–1.69 | Variable; use 1.55 as default estimate |
Source: standard geotechnical references; ASTM D698 (Standard Proctor) defines the dry density basis. Wet fill weighs more — add 5–15% for in-place moisture.
How Many Truckloads of Fill Dirt?
A standard single-axle dump truck holds about 10 cubic yards. Divide your compaction-adjusted cubic yards by your truck's capacity and round up — suppliers don't deliver fractional loads.
| Truck Type | Capacity (cu yd) | Best For |
|---|---|---|
| Standard single-axle | 10 | Most residential projects under 30 cu yd |
| Tandem axle | 12–14 | Medium grading jobs, 30–60 cu yd |
| Tri-axle | 15–16 | Large fill jobs over 60 cu yd |
Worked Example: 40 × 20 ft Backyard at 6 in
Fill Dirt for Sloped or Irregular Areas
For a sloped area where one end sits at grade and the other needs fill up to a maximum depth, the cross-section is a triangle — use the wedge formula. The calculator's slope mode applies this automatically.
Worked Example: 40 × 20 ft, 18 in Deep at Low End
Fill Dirt vs. Topsoil — What's the Difference?
Fill dirt is unscreened subsoil with no organic matter, used to build up grade and support structures. Topsoil is the nutrient-rich upper layer used for planting and lawn establishment. They are not interchangeable — fill dirt cannot support plant growth, and topsoil cannot reliably support structural loads.
| Property | Fill Dirt | Topsoil |
|---|---|---|
| Organic matter | Minimal (often none) | High (typically 2–10%) |
| Primary use | Structural grade-up, foundation backfill, retaining walls | Planting, lawn establishment, garden beds |
| Compaction | Compacts to stable load-bearing surface | Compacts poorly; stays loose for root growth |
Need topsoil for planting? Use our Topsoil Calculator instead. Many projects layer both — fill dirt to build grade, then 4–6 inches of topsoil on top.
Use Case Guide: How Much Fill Dirt by Project Type
How much fill dirt you need depends on the project type, which dictates depth, soil specification, and whether compaction matters. The decision matrix below maps the seven most common residential and light-commercial fill projects.
| Project Type | Typical Depth | Fill Type | Compaction? | Notes |
|---|---|---|---|---|
| Yard leveling | 3–6 in | General fill | No (light tamp OK) | Not load-bearing |
| Foundation grade-up | 6–12 in | General fill | Yes — 4 in lifts | Critical for drainage |
| Garden bed base | 4–8 in | Clean / sandy fill | No | Topsoil needed on top |
| Retaining wall backfill | Varies | Structural fill + gravel | Yes — 95% Proctor per ASTM D698 | Engineer for walls > 4 ft |
| Driveway subbase | 6–12 in | Granular structural | Yes — multiple lifts | Must meet road-base spec |
| Under concrete slab | 4–6 in | Granular / gravel | Yes — well-compacted | Prevents cracking |
| Trench backfill | Full depth | Match existing soil | Yes — 8 in lifts | Prevents sinkholes |
Fill Dirt for Yard Leveling
Typical depths run 3 to 6 inches. A 15% compaction buffer is appropriate even for non-load-bearing surfaces, because the dirt settles under foot traffic and irrigation cycles. For a 20 × 30 ft low spot at 4 inches average depth: 20 × 30 × 0.333 ÷ 27 = 7.4 cu yd base, or 8.5 cu yd with the 15% buffer.
Fill Dirt for Foundation Backfill
Foundation backfill builds positive drainage away from the building. Depths usually run 6 to 12 inches, sloped at least 6 inches over the first 10 feet from the foundation per IRC R401.3 grading guidance. Compact in 4-inch lifts. Avoid placing clay directly against the foundation wall — expansive clay swells with moisture and can crack masonry.
Fill Dirt for Retaining Wall Backfill
Retaining wall backfill is engineered fill. ASTM D698 defines the compaction spec — typically 95% maximum dry density. Place 8 to 12 inches of drainage gravel directly behind the wall, then structural fill in 4 to 6 inch lifts beyond the gravel zone. For walls over 4 ft, also size the footing with our concrete calculator and the drainage layer with our gravel calculator.
When the Calculator Formula Is Not Enough
The L × W × D ÷ 27 formula covers residential yard leveling and routine grading. In the situations below, call a geotechnical engineer before ordering fill dirt.
When to Call a Geotechnical Engineer
- •Structural applications — retaining walls over 4 ft, building foundations, slabs carrying load
- •Significant quantities — over 100 cubic yards (10+ truckloads in a single placement)
- •High-plasticity clay subsoils — expansive clay means fill compaction specs matter and a soil report is warranted
- •Proximity to property lines or structures — improper grading can cause drainage disputes or structural damage
- •Regulated sites — many municipalities require an engineer's stamp for grading above 50 cubic yards or 4 feet of fill height
— Alex Rivera, PE, CalcSummit Engineering Reviewer
Fill Dirt Cost and Delivery Estimates
Fill dirt costs roughly $15 to $55 per cubic yard delivered in most US markets as of May 2026, with the median around $25 to $30. Unscreened bulk fill from a local quarry sits at the lower end; screened fill runs $35 to $55 per yard. Add delivery fees of $50 to $150 per trip within a 15-mile radius.
- Travel distance — fill dirt is heavy; freight dominates cost. Suppliers within 5 miles often quote a flat trip fee.
- Screened vs. unscreened — screened fill costs more (rocks and roots removed).
- Soil type — sandy granular fill commands a premium in scarce markets; clay-heavy fill is cheaper.
- Season — spring grading season (Apr–Jun) pushes prices up 10–25%. Late summer or fall is often cheaper.
- Quantity — orders under 5 cu yd sometimes carry a short-load fee; orders over 20 cu yd often negotiate down per yard.
Cost data last updated: May 2026. Refreshes quarterly.