You marked a 4-foot grade change on the plan. Now you need one foot of fill in the low zone. How many yards? How many tons? Rock or dirt?
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Volume first
For a simple pad (length × width × depth in feet), divide by 27 for cubic yards.
Example: 40 ft × 30 ft × 1 ft = 1,200 cu ft ÷ 27 ≈ 44.4 cubic yards
Add shrink/swell: compacted fill often needs 10–15% extra loose volume depending on material and moisture.
Rock versus dirt
| Material | Loose lb/cu ft (typical) | Notes |
|---|---|---|
| Common fill dirt | 90–110 | Compacts with moisture |
| Clean gravel / #57 | 95–105 | Drains well, less shrink |
| Limestone riprap | 100–120 | Heavier, armoring slopes |
Tons ≈ (cubic yards × 27 × density lb/cu ft) ÷ 2,000
44.4 yd³ of dirt at 100 lb/cu ft ≈ 60 tons loose before compaction.
Slope check
On a 4-foot rise over run R, slope percent = (4 ÷ R) × 100. Steeper slopes need shorter bench lifts — do not place a full foot of loose fill on bare clay and walk away.
Order one truck at a time until your stakes agree with your tape. Math is cheap; regrading is not.