Calculator Inputs
Metric mode expects cable weight in kg/m. Imperial mode expects cable weight in lb/ft.
Formula Used
This calculator combines straight-run resistance, slope effect, and bend amplification. It is useful for quick pull-planning estimates.
Metric only: Fw = w × g
Tstraight = Tentry + (Fw × L × (μ × cos α + sin α))
Texit = Tstraight × e^(μ × θ)
Tdesign = Texit × Safety Factor
Psidewall = Tstraight ÷ R
- w = cable weight per unit length
- g = 9.80665 m/s²
- L = route length
- μ = friction coefficient
- α = slope angle
- θ = total bend angle in radians
- R = minimum bend radius
How to Use This Calculator
- Select metric or imperial units.
- Enter cable weight per unit length.
- Enter the full pulling route length.
- Add the expected friction coefficient.
- Enter the total accumulated bend angle.
- Enter entry tension, slope angle, safety factor, allowable tension, and minimum bend radius.
- Click Calculate Tension to show results above the form.
- Review the graph, utilization, margin, and export options.
Example Data Table
| Scenario | Unit | Weight | Length | μ | Bend Angle | Slope | Safety Factor | Design Tension | Status |
|---|---|---|---|---|---|---|---|---|---|
| Conduit Pull A | Metric | 3.20 kg/m | 120.00 m | 0.35 | 180° | 5° | 1.25 | 6723.37 N | Within Limit |
| Conduit Pull B | Imperial | 1.80 lb/ft | 350.00 ft | 0.28 | 270° | 2° | 1.20 | 2950.00 lbf | Check Allowable |
Frequently Asked Questions
1. What is cable pulling tension?
Cable pulling tension is the force required to move cable through a route. It rises with length, friction, bends, and uphill sections. Staying below the allowable value helps reduce insulation damage and conductor stress.
2. Why do bends increase tension quickly?
Bends amplify incoming tension through capstan action. Even moderate friction can produce a large increase when the cable wraps through several bends. That is why accumulated angle matters so much in route planning.
3. What friction coefficient should I use?
Use the best available value from lubricant data, conduit material, cable jacket material, or manufacturer guidance. Conservative estimates are safer when field conditions are uncertain or when route cleanliness is questionable.
4. How does slope affect pulling force?
Uphill pulls add gravitational resistance, which raises tension. Downhill pulls can reduce required pulling force. Enter a negative slope angle for downhill sections in this calculator.
5. What is sidewall pressure?
Sidewall pressure estimates how strongly the cable presses against a bend. High values can damage the jacket or conduit contact surface, so installers often review this value along with total tension.
6. Should the allowable tension come from the manufacturer?
Yes. Use the cable manufacturer’s maximum allowable pulling tension whenever possible. That value is more reliable than a generic estimate and should guide your pass or fail decision.
7. Does this calculator replace a full engineering pull study?
No. This tool gives a fast planning estimate. Complex routes, multiple pull points, special lubricants, segmented bends, and installation code requirements may require a more detailed engineering review.
8. Why apply a safety factor?
A safety factor helps cover uncertainty in field friction, route condition, bend quality, and handling variability. It gives a more conservative design tension for planning and decision support.