Formula Used
The calculator estimates volume from canal length and cross-sectional area.
For a trapezoidal section:
- Top width:
t = b + 2·s·d
- Area:
A = (b + t) / 2 · d
- Bank volume:
V = A · L
For a rectangular section, t = b. For a triangular section, b = 0.
Optional factors apply after the bank volume:
- Over-excavation:
Vₐ = V · (1 + p/100)
- Loose volume:
Vₗ = Vₐ · (1 + swell/100)
- Compacted volume:
V𝚌 = Vₐ · (1 − shrink/100)
How to Use This Calculator
- Select a section shape that matches your canal design.
- Choose a section method to define the geometry.
- Enter length and section dimensions in one unit system.
- Add optional freeboard and over-excavation allowances.
- Set swell and shrink for material handling estimates.
- Click Calculate to view results above the form.
- Use Download CSV/PDF to export the latest results.
Example Data Table
| Shape |
Method |
Length (m) |
Depth (m) |
Bottom (m) |
Side Slope (H:V) |
Over-exc (%) |
Swell (%) |
Bank Vol (m³) |
Loose Vol (m³) |
| Trapezoidal |
Side slope |
250 |
2.0 |
1.5 |
1.5 |
5 |
20 |
1562.500 |
1968.750 |
| Rectangular |
Top width |
120 |
1.2 |
2.0 |
— |
0 |
10 |
288.000 |
316.800 |
Example values are illustrative. Real projects should follow design drawings,
specifications, and local measurement standards.
Professional Article
Canal excavation quantity drives budgeting, equipment selection, hauling logistics, and project scheduling.
Small errors in channel geometry can create large volume differences over long alignments, so this tool
focuses on clear inputs and repeatable calculations. Use it during early estimating, then refine values
as survey data and design drawings mature.
Start by confirming the section definition used on your plans. Many canals are trapezoidal for stability
and maintenance access, while rectangular sections appear in lined channels, culverts, and constrained corridors.
If you know the side slope (horizontal to vertical), the calculator derives the top width automatically.
If the top width is specified directly, select the corresponding method to match the drawing.
The “bank volume” represents in-situ excavation. For operations, material often expands after digging
(swell), and later reduces when placed and compacted (shrink). These optional factors convert bank volume
into loose and compacted quantities, helping you plan truck loads, stockpile space, and backfill targets.
Over-excavation and freeboard allowances can also be applied when tolerances, trimming, or contingency
quantities are expected.
Example (trapezoidal): Length 250 m, depth 2.0 m, bottom width 1.5 m, side slope 1.5H:1V,
over-excavation 5%, swell 20%. The derived top width is 7.5 m and the area is 9.375 m². Bank volume becomes
2343.750 m³, and bank with allowances is 2460.938 m³. Loose volume is 2953.125 m³ after swell. These values
align with the sample table and demonstrate how allowances and handling factors change planning quantities.
For best results, keep units consistent, verify whether depths include any freeboard or lining thickness,
and document the assumptions used for swell and shrink. When specifications provide material-specific
factors, prefer those over generic percentages. Good quantity records improve cost control and reduce
disputes during measurement and payment.
FAQs
1) What is the difference between bank, loose, and compacted volume?
Bank volume is the in-place excavation quantity. Loose volume accounts for expansion after digging (swell).
Compacted volume estimates the reduced quantity after placement and compaction (shrink).
2) Which method should I choose for section geometry?
Use “side slope” when drawings specify H:V slopes. Use “top width” when both bottom and top widths are stated.
Use “area (direct)” when a surveyed cross-sectional area is already calculated.
3) How should I select a swell percentage?
Swell depends on soil type, moisture, and excavation method. Use project specifications or geotechnical guidance
when available. If unknown, run sensitivity checks with low, medium, and high values to understand risk.
4) What does shrink percentage represent here?
Shrink represents the volume reduction from bank to compacted condition. It is a simplified estimate for planning.
For controlled fills, compaction test results and specification requirements provide better factors.
5) Why is freeboard included as an allowance?
Freeboard is an optional extra depth added for tolerance, trimming, or planning. If your design depth already
includes this margin, leave freeboard at zero to avoid double counting.
6) Can I use this calculator for lined canals?
Yes. Enter the excavation geometry, then separately account for lining thickness and bedding if required.
For rectangular lined channels, the “top width” method often matches design drawings best.
7) How can I document results for a measurement sheet?
After calculating, download the CSV or PDF and attach it to your quantity takeoff. Note the section type,
method, unit system, and any swell, shrink, or allowance assumptions used for transparency.
Accurate canal volumes improve schedules, costs, and site safety.