Fill Dirt Calculator
Calculate fill dirt for grading and backfill. Enter values for instant results with step-by-step formulas.
Formula
Loose Volume = Compacted × (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 × 4 = 320 sq ft Depth: 2 ft Compacted volume: 320 × 2 = 640 cu ft 640 ÷ 27 = 23.7 yards Loose (20% compaction): 23.7 × 1.20 = 28.4 yards Order: 29-30 cubic yards
Result:Order 30 cubic yards fill dirt
Example 2: Level Yard
Problem:Low area 30×40 ft needs 8" fill to level with rest of yard.
Solution:Area: 30 × 40 = 1,200 sq ft Depth: 8" = 0.667 ft Compacted: 1,200 × 0.667 = 800 cu ft 800 ÷ 27 = 29.6 yards Loose (25%): 29.6 × 1.25 = 37 yards Trucks: 4 loads
Result:37 yards (4 truckloads)
Example 3: Driveway Base
Problem:Driveway 50×12 ft needs 4" compacted stone base.
Solution:Area: 50 × 12 = 600 sq ft Depth: 4" = 0.333 ft Compacted: 200 cu ft = 7.4 yards Loose (15% for crushed stone): 7.4 × 1.15 = 8.5 yards Order: 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 × (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.
What is structural fill?
Engineered fill for areas supporting structures: foundations, under slabs, retaining walls. Must meet compaction specifications (usually 95% Standard Proctor). Often specified as select fill, crushed stone, or flowable fill. Requires testing. Not regular fill dirt.
How do I compact fill dirt?
Hand tamper: Small areas, thin lifts. Plate compactor (vibratory): Most DIY projects, up to 8" lifts. Jumping jack: Trenches, tight spaces. Roller: Large areas, professional work. Water helps compaction but don't saturate. Make multiple passes per lift.
Will fill dirt settle over time?
Yes, if not properly compacted. Poorly compacted fill can settle 10-30% over months/years, causing foundation cracks, slabs to sink, pavement damage. Proper compaction (95%+ for structural areas) minimizes future settlement. Allow time for natural settlement on non-critical fills.
What about drainage in fill areas?
Fill dirt must drain properly. Clay soils hold water - create wet, unstable base. Good fill: sandy loam, gravel. For foundation backfill: use free-draining material within 12-18" of foundation, then fill dirt beyond. Ensure positive drainage away from structures.