Wire & Cable calculator
Cable Pulling Tension Calculator
Use this cable pulling calculator when you need to enter the run length, cable weight, bend angle, friction coefficient, conductor size, and bend radius before deciding whether a pull needs lubricant, larger sweeps, a pull box, or a revised pull direction. The calculator compares total pulling tension, conductor tension limits, and sidewall pressure for the route you enter.
Updated July 16, 2026
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Pulling supplies for cable runs
After estimating tension and sidewall pressure, compare pulling supplies that support the physical pull plan.
Compare fish tapesFor routing conductorsOpens in a new tabFind pulling lubricantMatch cable jacket useOpens in a new tabCompare pulling gripsFor controlled pullsOpens in a new tab
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How to Use
Cable Pulling Tension Calculator for Route-Specific Pull Plans
Start with the calculator before copying a field example. Enter the route length, cable weight, bend angle, friction condition, conductor material, conductor size, and tightest bend radius so the pulling-tension and sidewall-pressure check matches your installation.
Reference After You Calculate: Common Planning Limits
| Material | Max Tension | Use In Calculator |
|---|---|---|
| Copper (soft drawn) | 8 lbs/kcmil | Select conductor size so the tool applies the kcmil limit. |
| Aluminum (1350) | 4 lbs/kcmil | Select conductor size so the tool applies the kcmil limit. |
Maximum Sidewall Pressure: 500 lbs/ft (typical for most insulations)
Cable Pulling Tension Formula
T = W × μ × e^(μθ)
Where:
- T = Pulling tension (lbs)
- W = Cable weight (lbs)
- μ = Coefficient of friction (0.15-0.50)
- θ = Total bend angle (radians)
Friction Coefficients
| Condition | μ Value |
|---|---|
| Lubricated PE/PVC | 0.15 |
| Unlubricated PE/PVC | 0.25 |
| Rubber/XLPE | 0.35 |
| Dry conditions | 0.50 |
For conduit fill requirements, use Conduit Fill Calculator.
Try a Pulling Tension Example in the Calculator
Use the example inputs for a feeder pull with a long route, large copper conductors, cumulative bends, and an unlubricated friction assumption, then calculate to see the route-specific pulling tension, conductor-limit comparison, and SWP check. Keep the result with the route sketch and cable submittal before sending the crew to the pull.
After the calculator result, continue with the Cable Pulling Tension Chart for crew notes, the Pull Box Sizing Calculator when the route needs a pull point, the Wire Size Calculator for conductor selection, the Ampacity Calculator for thermal limits, and the Voltage Drop Calculator for long-run performance.
Technical notes. Open for formula basis, assumptions, and validation notes.
The Physics of Cable Pulling: The Exponential Threat of Bends
Pulling tension does not increase linearly as cable passes around bends; each bend multiplies the incoming tension according to the capstan equation: Tout = Tin × e(μθ). If a straight 100-foot section requires 100 lb of tension, adding a 90-degree sweep (π/2 radians) with a PVC friction coefficient of 0.35 multiplies the incoming tension by about 1.73. Three 90-degree bends can multiply the tension by roughly 5.2. That is why pull direction, lubricant, sweep radius, and intermediate pull points should be reviewed before large conductors are installed.
Real-World Mechanics: Sidewall Bearing Pressure (SWP)
Total pulling tension checks conductor tensile limits, while Sidewall Bearing Pressure (SWP) checks the radial force applied to cable insulation at bends. SWP is calculated by dividing pulling tension at the bend by bend radius (T/R). A pull can stay below the conductor tension limit and still create excessive pressure at a tight bend, so the calculator reviews both values. Confirm the final allowable SWP with the cable manufacturer and project specifications.
NEC 300.18: The "Pull-After-Install" Mandate
NEC 300.18(A) requires raceways to be complete between outlets, boxes, or fittings before conductors are installed. That keeps the pull path defined before tension and sidewall pressure are evaluated. For conductors 4 AWG and larger, NEC 314.28 also affects pull-box dimensions and spacing. Use the pull-box sizing workflow when the route needs an intermediate pull point, splice point, or access location.
Common Applications
More applications. Open to review 2 additional use cases.
Frequently Asked Questions
Why does pulling tension increase exponentially with bends?
Each bend multiplies the tension by e^(μθ). Two 90° bends do not just double the tension - they multiply it by about 2.2× with typical friction. This is why minimizing bends is critical for long pulls.
How do I reduce cable pulling tension?
Key strategies: 1) Use cable pulling lubricant (reduces μ from 0.5 to 0.15), 2) Install pull boxes to break up long runs, 3) Use larger conduit (less cable-to-wall contact), 4) Pull from the end with most bends.
What is sidewall pressure and why does it matter?
Sidewall pressure (SWP) is the crushing force on cable at bends. High SWP can damage insulation even if total tension is OK. Most cables limit SWP to 500 lbs/ft. Use larger radius bends or factory sweeps to reduce SWP.
Should I pull from the beginning or end of the run?
Pull from the end with the most bends. Bends multiply tension, so the lowest tension should be at the start of the pull where it will be multiplied the most times.
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