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Conduit Bending calculator

Concentric Bend Spacing Calculator

Professional concentric bend spacing calculator for parallel conduit racks. Calculates center-to-center spacing, mark offsets for each conduit, and total rack width for any number of parallel conduits. Ensures all conduits line up perfectly after bending — inner to outer — for professional-looking installations.

Updated June 21, 2026

Calculator Inputs

Total conduits in the parallel run

Radius of innermost conduit bend (inches)

Gap between conduit faces (inches)

Calculation Results

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Example Calculations

4 Parallel ¾" EMT at 90°

Standard parallel rack with ½" spacing.

Inputs
  • Number Of Conduits: 4
  • Conduit Type: EMT
  • Conduit Size: 3/4 in.
  • Bend Angle: 90 degrees
  • Spacing: 0.5

How to Use

Parallel Conduit Bending: Making Racks Look Professional

When bending multiple parallel conduits, each pipe needs different mark positions because outer conduits travel a longer arc around the bend. If you use the same marks for all pipes, the outer ones come up short or the rack spacing changes after the bend. This calculator provides the exact mark adjustment for each conduit position.

Center-to-Center Spacing Formula

C-C = Conduit OD + Desired Gap

Trade Size EMT OD C-C (½" gap) IMC OD C-C (½" gap)
½"0.706"1.206"0.815"1.315"
¾"0.922"1.422"1.029"1.529"
1"1.163"1.663"1.290"1.790"
1¼"1.510"2.010"1.638"2.138"
1½"1.740"2.240"1.883"2.383"
2"2.197"2.697"2.360"2.860"

Mark Offset Calculation for 90° Bends

For a 90° bend, each outer conduit needs its mark moved back by a fixed offset per conduit position:

Mark Offset = Position Number × C-C × (π/4)

Where π/4 ≈ 0.7854 (the difference in arc length per center-to-center of spacing at a 90° bend).

Conduit # ¾" EMT (C-C 1.422") 1" EMT (C-C 1.663") 1½" EMT (C-C 2.240")
#1 (Inner)Reference (0")Reference (0")Reference (0")
#2+1.12"+1.31"+1.76"
#3+2.23"+2.61"+3.52"
#4+3.35"+3.92"+5.28"
#5+4.47"+5.22"+7.04"
#6+5.58"+6.53"+8.79"

Worked Example: 4-Conduit ¾" EMT Rack — 90° Bend

A rack of 4 × ¾" EMT conduits needs a 90° bend. Inner conduit stub-up mark at 12":

  • Conduit #1 (inner): Mark at 12.00" — reference
  • Conduit #2: Mark at 12.00" + 1.12" = 13.12"
  • Conduit #3: Mark at 12.00" + 2.23" = 14.23"
  • Conduit #4 (outer): Mark at 12.00" + 3.35" = 15.35"

Bend from inner to outer. Always bend the innermost conduit first and work outward. This allows you to check alignment after each bend and adjust before committing the next pipe.

Pro Tips for Clean Parallel Racks

  • Cut all conduits to the same length before bending — this ensures the rack ends line up perfectly after the bends
  • Color-code or number each conduit to avoid mixing up the different mark positions
  • Use strut and clamps to hold the first bent conduit in place as a reference while bending subsequent pipes
  • Check alignment every bend — it's far easier to correct a slight error on the second conduit than to re-bend the fourth
  • Deburr after cutting — burrs on the ends make the conduit sit unevenly in the straps, ruining the professional appearance

Common Applications

Conduit rack 90° bends — calculate mark offsets for 2–8 parallel conduits making a 90° turn

Parallel offset bends — adjust marks for multiple conduits making identical offsets in a rack

Commercial electrical distribution — design professional-looking exposed conduit racks

Industrial plant installations — large-scale parallel conduit arrays for motor control and distribution

Panel feed conduit — multiple conduits entering panel boards or switchgear side-by-side

MCC and switchgear feed — parallel feeders from transformers to motor control centers

Data center power distribution — parallel conduit runs under raised floors and overhead cable trays

Equipment room routing — maintain uniform conduit spacing through multiple direction changes

Frequently Asked Questions

Why do outer conduits need different marks than inner conduits?
Each conduit in a parallel rack bends around a different radius. The inner conduit has the tightest radius (standard bender radius), while each outer conduit bends around a progressively larger radius (adding one center-to-center distance per position). A larger bend radius means a longer arc length, so the outer conduits need their marks moved further from the end of the conduit. Without this offset adjustment, outer conduits will be short after bending and the rack spacing will collapse at the bend.
What gap should I use between parallel conduits?
Standard practice is ½" (12mm) between conduit faces, making center-to-center = conduit OD + ½". This gap allows for: thermal expansion, clearance for couplings and connectors, easier wire pulling, and access for strap installation. Some project specifications require different spacing — check your drawings. For Unistrut-mounted racks, spacing is determined by the clamp width. For very large conduit (2" and above), ¾" to 1" gaps are common because the larger couplings need more clearance.
Do I need to adjust the bender setting for each conduit?
No — use the same bender and same bend angle (90° or whatever your design requires) for all conduits. The only thing that changes is where you mark each conduit. The bender shoe radius stays the same, which is why the mark offset formula works. However, for conduits in positions 5+ in a large rack, verify that the bender can physically accommodate the conduit at the adjusted mark position — very long stubs may exceed the bender handle length.
How do I handle offsets (not 90° bends) in parallel conduit runs?
For parallel offsets, the principle is the same: each outer conduit needs its marks adjusted. The offset height is identical for all conduits (they must all clear the same obstacle), but the distance between marks increases for outer conduits. Calculate the inner conduit's marks normally, then add the concentric spacing offset for each outer position. The offset adjustment per conduit is proportional to the center-to-center distance and depends on the bend angle used for the offset.
What order should I bend conduits in a parallel rack?
Always bend from the inside out: inner conduit first, then work progressively to the outer conduit. Reasons: (1) the inner conduit serves as your reference for checking alignment of subsequent bends; (2) if you make an error, it's easier to correct early — an error on the inner conduit affects all subsequent pipes; (3) you can physically hold each new pipe against the previously bent ones to verify fit before permanently strapping. After bending, install straps and supports before proceeding to the next conduit to maintain perfect spacing throughout the rack.

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