Formula
Loose Volume = Compacted Γ (1 + Compaction %)
Calculate compacted volume needed, then add compaction factor to determine loose volume to order. Soil shrinks when compacted.
Worked Examples
Example 1: Backfill Foundation
Problem: Foundation perimeter 80 ft long, 4 ft wide trench, needs 2 ft of fill after foundation is set.
Solution: Area: 80 Γ 4 = 320 sq ft\nDepth: 2 ft\n\nCompacted volume:\n320 Γ 2 = 640 cu ft\n640 Γ· 27 = 23.7 yards\n\nLoose (20% compaction):\n23.7 Γ 1.20 = 28.4 yards\n\nOrder: 29-30 cubic yards
Result: Order 30 cubic yards fill dirt
Example 2: Level Yard
Problem: Low area 30Γ40 ft needs 8\" fill to level with rest of yard.
Solution: Area: 30 Γ 40 = 1,200 sq ft\nDepth: 8\" = 0.667 ft\n\nCompacted: 1,200 Γ 0.667 = 800 cu ft\n800 Γ· 27 = 29.6 yards\n\nLoose (25%):\n29.6 Γ 1.25 = 37 yards\n\nTrucks: 4 loads
Result: 37 yards (4 truckloads)
Example 3: Driveway Base
Problem: Driveway 50Γ12 ft needs 4\" compacted stone base.
Solution: Area: 50 Γ 12 = 600 sq ft\nDepth: 4\" = 0.333 ft\n\nCompacted: 200 cu ft = 7.4 yards\n\nLoose (15% for crushed stone):\n7.4 Γ 1.15 = 8.5 yards\n\nOrder: 9 cubic yards
Result: Order 9 yards crushed stone
Frequently Asked Questions
What is fill dirt?
Fill dirt is subsoil (no organic matter) used to raise ground level or fill holes. Different from topsoil (has organic matter for plants). Fill dirt compacts well and doesn't decompose. Common uses: foundation backfill, grading, raising low areas.
How does compaction affect fill quantity?
Fill dirt compacts 15-30% after placement and compaction. Order loose volume = compacted volume Γ (1 + compaction %). Example: need 10 compacted yards, with 20% compaction = 12 loose yards to order. Otherwise you'll be short after compacting.
Clean fill vs regular fill dirt?
Clean fill: free of debris, organic matter, contaminants. Passes through screen, suitable for building sites. Regular fill: may contain rocks, roots, some debris. Cheaper but may not meet code for structural backfill. Use clean fill near foundations.
How much does fill dirt cost?
Bulk fill dirt: $10-50 per cubic yard depending on quality and location. Delivery: $50-150. Topsoil costs more ($20-80/yard). Free fill sometimes available from excavation sites - you pay delivery/loading. Small bags at stores are very expensive per volume.
How deep can I fill in one layer?
Compact in lifts (layers) of 6-12 inches. Thicker layers won't compact properly in center. For deep fills: place 8\" lift, compact, repeat. Proper compaction prevents future settling. Use plate compactor or roller for each lift.
Can I use excavated soil as fill?
If it's good soil (not topsoil, clay, or organic), yes. Test: compact a handful - if it clumps and holds shape (clay), it's poor fill. If it crumbles, it's good. Remove rocks over 3-4 inches. Clay and organic soils are poor fill choices.
Background & Theory
The Fill Dirt Calculator applies the following established principles and formulas.
Structural and construction engineering is governed by fundamental load analysis, material science, and regulatory standards that ensure the safety and durability of built structures. The primary distinction in load analysis is between dead loads β the permanent self-weight of structural elements, finishes, and fixed equipment β and live loads, which represent variable occupancy, furniture, and environmental forces such as wind and snow. These are combined using factored load equations, such as the ASCE 7 formula U = 1.2D + 1.6L, where D is dead load and L is live load. Concrete mix design is governed by the water-cement (w/c) ratio, which is the primary determinant of compressive strength and durability. A w/c ratio of 0.40β0.45 typically yields concrete with 28-day compressive strengths of 30β40 MPa. Common mix ratios by weight for structural concrete are approximately 1 part cement : 1.5β2 parts sand : 3 parts coarse aggregate. Structural steel is characterized by its yield strength (the stress at which permanent deformation begins, typically 250β350 MPa for mild steel) and ultimate tensile strength (typically 400β500 MPa). Mid-span deflection of a simply supported beam under a central point load is given by Ξ΄ = FLΒ³ / (48EI), where F is force, L is span length, E is Young's modulus, and I is the second moment of area. Building insulation is rated by R-value, a measure of thermal resistance in units of mΒ²Β·K/W (SI) or ftΒ²Β·Β°FΒ·h/BTU (imperial). Higher R-values indicate greater resistance to heat flow. Foundation design depends on the allowable bearing capacity of the underlying soil, which ranges from approximately 75 kPa for soft clay to over 10,000 kPa for bedrock. Drainage gradients for surface water are typically specified as a minimum of 1β2% slope away from building foundations to prevent hydrostatic pressure and water infiltration.
History
The history behind the Fill Dirt Calculator traces back through the following developments.
The history of construction engineering spans thousands of years of accumulated empirical knowledge and, more recently, rigorous scientific analysis. The ancient Egyptians built the Great Pyramid of Giza around 2560 BCE using an estimated 2.3 million stone blocks, demonstrating sophisticated logistics, geometry, and workforce organization. Roman engineers advanced the field dramatically through the use of pozzolanic concrete β a mixture of volcanic ash, lime, and seawater β enabling the construction of the Pantheon dome (43.3 m diameter, completed around 125 CE) and a vast network of aqueducts and roads across the empire. Cast iron emerged as a structural material during the Industrial Revolution, first used prominently in the Iron Bridge at Coalbrookdale, England, completed in 1779. Wrought iron and later steel allowed far greater spans and heights. The Eiffel Tower, completed in 1889, demonstrated the structural possibilities of wrought iron at scale and influenced the development of steel-frame skyscraper construction in Chicago and New York. Reinforced concrete was systematically developed by Joseph Monier, a French gardener, who patented iron-reinforced concrete pots and panels in the 1860s, and later by engineers including FranΓ§ois Hennebique who created the first comprehensive reinforced concrete framing system in the 1890s. The 1906 San Francisco earthquake caused widespread devastation and galvanized the engineering profession to develop seismic design provisions. Subsequent earthquakes β including the 1971 San Fernando and 1994 Northridge events β drove successive improvements in seismic codes, base isolation technology, and ductile detailing of reinforced concrete and steel frames. Building codes became increasingly standardized in the twentieth century, with the International Building Code (IBC) first published in 2000 providing a unified model code adopted across much of the United States. Building Information Modeling (BIM) emerged in the 2000s as a digital workflow integrating architectural, structural, and MEP design into a unified three-dimensional model, fundamentally changing coordination practices across the industry.