Cut and fill calculations compare existing field elevations to design elevations to determine how much material to excavate (cut) or add (fill). Average end area method: V = (A1 + A2) ÷ 2 × L, where A1 and A2 are cross-sectional areas (sq ft), L is distance between sections (ft), and result is cubic feet (divide by 27 for cubic yards).
Why These Calculations Drive the Job
Before a single blade cut, you need to know how much material moves and which direction. Cut and fill calculations drive the haul plan, borrow material requirements, spoil disposal plan, and daily production targets. Underestimate fill needs and you run short at the end of the job. Overestimate cut and you pay to haul material you should have kept. Either way costs money.
Step 1: Take Field Elevations at a Grid
Grid density depends on terrain complexity:
- Flat to gently rolling: 50-ft grid usually sufficient.
- Moderate terrain: 25-ft grid, plus shots at slope breaks — ridgelines, swales, drainage edges.
- Rough or hilly: 25-ft or denser, with shots at all significant terrain features.
Work through the grid row by row. Record each point with a station identifier and elevation. Use the Elevation Calculator to verify your HI before beginning.
Step 2: Get Design Elevations at Each Grid Point
Read finished grade elevations from the grading plan at each grid point. A spreadsheet with existing elevation, design elevation, and the difference at each point is the standard format:
Point A-2: Existing 105.80 | Design 105.00 | −0.80 ft (CUT)
Point A-3: Existing 105.10 | Design 105.00 | −0.10 ft (CUT)
Average End Area Method
Cut area at Sta 0+00: 45.2 sq ft | At Sta 0+50: 52.7 sq ft | Distance: 50 ft
V = (45.2 + 52.7) ÷ 2 × 50 = 2,448 cu ft = 90.7 cu yd
Use the Cut and Fill Calculator to compute volumes from your grid elevation data.
Shrinkage and Swell Factors
| Material | Swell (bank→loose) | Shrinkage (bank→compacted) |
|---|---|---|
| Clay | 1.25–1.40 | 0.85–0.90 |
| Sandy clay | 1.10–1.25 | 0.90–0.95 |
| Sand | 1.10–1.15 | 0.85–0.92 |
| Clean gravel | 1.05–1.15 | 1.00–1.05 |
| Blasted rock | 1.30–1.50 | 1.05–1.30 |
Balancing Cut and Fill
Compacted volume from cut: 3,200 × 0.90 = 2,880 cu yd
Fill needed (compacted): 2,600 cu yd
Excess to export: 2,880 − 2,600 = 280 cu yd
See also: Blue-Top Stakes: Setting and Reading Grade Stakes and Excavation Calculator.