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Electrical Duct Bank Concrete Calculator
Calculate the concrete envelope around a rectangular conduit bank from the dimensions on the electrical or utility detail. Conduit displacement is deducted before the ordering allowance is applied.
Calculate electrical duct bank concrete quantities
Use this duct bank concrete calculator when the conduit arrangement and concrete cover are already specified. Enter rows, conduits per row, actual conduit outside diameter, clear spacing, cover and run length to calculate the net concrete quantity.
Formula: Envelope width = columns × conduit OD + (columns − 1) × clear horizontal spacing + 2 × side cover. Envelope height = rows × conduit OD + (rows − 1) × clear vertical spacing + 2 × top/bottom cover. Net concrete = envelope volume − total conduit outside volume.
Measurement check: Use the actual outside diameter of the selected conduit, not its nominal trade size. Measure clear spacing between conduit exteriors, and take concrete cover from the project detail. Confirm whether the stated run length includes bends, transitions or changes in bank cross-section; calculate differing sections separately.
What the result includes: The gross rectangular envelope is reduced by the outside volume occupied by the conduits. The resulting net concrete quantity is shown separately from the user-selected ordering allowance. Envelope width and height are reported so they can be compared with the drawings before ordering.
Before ordering: Check duct count and arrangement, actual product outside diameter, top/bottom and side cover, specified reinforcement and any changes in section. The calculator assumes straight conduits with a uniform rectangular envelope along the entered length; it does not determine electrical separation, thermal performance, structural design or installation suitability.
Step 1
Enter project dimensions
Use dimensions from the applicable drawing, specification or field takeoff. Switch between US / Imperial and metric at any time; entered dimensions are converted automatically.
Step 2
Quantity result
Use project-specified geometry and material requirements. Allowance is shown explicitly rather than hidden inside the dimensions.
Worked example
The example uses the calculator's starting dimensions so the arithmetic can be checked independently.
Example inputs
| Duct bank length | 100 ft |
|---|---|
| Conduit rows | 2 count |
| Conduits per row | 3 count |
| Conduit outside diameter | 0.3333 ft |
| Clear horizontal spacing | 0.25 ft |
| Clear vertical spacing | 0.25 ft |
| Concrete cover each side | 0.25 ft |
| Concrete cover top and bottom | 0.25 ft |
| Concrete allowance | 5 % |
Example results
| Concrete to order | 8.982 yd³ |
|---|---|
| Net geometric concrete | 8.554 yd³ |
| Gross envelope | 10.493 yd³ |
| Conduit displacement | 1.939 yd³ |
| Envelope width | 2 ft |
| Envelope height | 1.417 ft |
How the calculation works
Envelope width = columns × conduit OD + (columns − 1) × clear horizontal spacing + 2 × side cover. Envelope height = rows × conduit OD + (rows − 1) × clear vertical spacing + 2 × top/bottom cover. Net concrete = envelope volume − total conduit outside volume.
Massachusetts highway-lighting standard drawings include typical conduit encasement under pavement and show that duct-bank envelope dimensions, duct arrangement and cover are detail-specific. Use the dimensions required by the project; this calculator does not design conduit spacing, cover or electrical capacity.
MassDOT — Standard Drawings for Traffic Signals and Highway Lighting
Scope: verify dimensions, material specifications, structural/electrical requirements, reinforcement, excavation support and local requirements independently. JobsiteMeasure estimates quantities; it does not design the installation.
Electrical Duct Bank Concrete Calculator FAQs
How is duct bank concrete volume calculated?
Calculate the rectangular concrete envelope from the specified conduit layout, spacing and cover, then subtract the outside volume occupied by every conduit.
Should I use nominal conduit size?
Use the actual outside diameter for the conduit product. Concrete is displaced by the physical outside of the conduit, not its nominal trade size.
Does this calculator choose conduit spacing or concrete cover?
No. Rows, spacing, cover, concrete specification and reinforcement are project-design inputs and must come from the applicable drawings and specifications.