Calculator
Choose a method, enter dimensions, then submit to calculate volumes. Use swell and allowance to estimate the dredged quantity for logistics.
Example data table
These sample scenarios show typical inputs and computed in-situ volume. Values are illustrative; confirm with your drawings and survey data.
| Scenario | Method | Key inputs | In-situ volume (m³) | Total with 10% swell + 5% allowance (m³) |
|---|---|---|---|---|
| Turning basin box cut | Rectangular | L=120 m, W=35 m, D=2.2 m | 9,240 | 10,692 |
| Access channel with 2H:1V slopes | Trapezoidal | Len=450 m, Bottom=18 m, Depth=1.8 m, Slope=2 | 22,356 | 25,871 |
| Two surveyed sections | Average end area | A1=42.5 m², A2=39.2 m², Dist=120 m | 4,902 | 5,673 |
Formula used
How to use this calculator
- Select units that match your drawings or survey outputs.
- Choose a method based on your available measurements.
- Enter dimensions carefully, using consistent units.
- Add swell and allowance to reflect handling and tolerance.
- Submit to view results above the form.
- Export the calculation as CSV or PDF for reporting.
Dredging quantity planning notes
1) What “volume” means on site
Projects typically track in-situ volume (cut in place), loose volume (after excavation), and measured volume (survey or contract method). This calculator estimates in-situ volume from geometry, then applies swell and allowance to reflect practical handling quantities. For bid comparisons, keep the same basis across all estimates.
2) Typical swell and tolerance ranges
Swell varies by material. Coarse sand may be 5–15%, while silty or mixed soils can be 15–30%. Allowance is often 2–10% to cover trimming, sloughing, and measurement tolerance. Match these inputs to your specs and recent production history. Clays may swell higher when remolded, while gravel typically stays lower.
3) Method selection by available data
Use Rectangular for uniform basins. Use Trapezoidal where side slopes define section shape. Use Average End Area when you have two surveyed cross-sections. Use Grid/Segments to model irregular footprints or varying depths across the work area.
4) Channel geometry and slopes
Trapezoids expand with depth: the top width increases by 2 × slope × depth. A 2H:1V slope at 2.0 m depth adds 8.0 m to top width, which can greatly change volume on long channels. Confirm if slopes apply on both sides and whether benches exist.
5) Grid sizing for better accuracy
Grid/Segments accuracy improves with smaller cells. Field teams often use 10–25 m spacing for broad areas and 5–10 m where grades change fast. Add more rows near edges, berth faces, and transitions to reduce under- or over-estimation.
6) Density and mass checks
If density is entered, the calculator estimates tonnes. Many sands and silts fall roughly around 1.4–1.8 t/m³, but values can vary by moisture and grading. Use lab results, geotechnical reports, or calibrated site measurements for reliable haul and disposal planning.
7) Production planning and cycle time
Translate total volume into time using realistic production and downtime. Smaller mechanical setups may average 80–200 m³/day depending on access and disposal distance. Add weather, maintenance, and traffic constraints so your schedule reflects achievable outputs, not ideal conditions.
8) Reporting and audit trail
Export CSV for an audit trail: method, survey date, unit basis, swell, allowance, and key assumptions. This record helps reconcile planned quantities with measured surveys and supports quicker review during progress meetings, payment checks, and variation discussions. Attach the export to daily logs so assumptions stay visible months later.
FAQs
1) Which method should I use for a turning basin?
Start with Rectangular if the basin is uniform. If depths vary, split the basin into segments or a grid so each cell reflects its own average cut depth.
2) What swell percentage is reasonable?
Many projects use 5–15% for sands and 15–30% for finer or mixed materials. Use your specs and recent production records; apply conservative values when disposal logistics are tight.
3) Does the allowance replace swell?
No. Swell estimates loose volume after excavation. Allowance covers tolerances, trimming, and irregularity. Apply swell first, then allowance, to estimate total handling quantity.
4) Can I enter areas in feet squared?
Yes. Switch Units to Imperial and input areas in ft² for Average End Area. The calculator converts internally and still reports results in m³, yd³, and ft³.
5) How many grid rows should I add?
Add enough rows to capture shape and depth changes. More, smaller cells usually improve accuracy. Focus extra rows near edges, slopes, and transitions where grades change quickly.
6) Why does density matter?
Density converts volume into tonnes, which helps with trucking limits, barge payload, and disposal fees. Use lab or geotechnical data when possible for realistic mass estimates.
7) Are these results suitable for final payment quantities?
Use them for planning and estimating. Final payment usually relies on contract measurement rules and survey surfaces. Keep exports and assumptions to support discussions with the client and engineer.