Cable Force Calculator

Welcome to this engineering tutorial where we will explore the fascinating world of cable forces and their calculator. Cable forces play a critical role in various engineering applications, including suspension bridges, cable-stayed structures, and elevator systems. In this tutorial, we will discuss the topic, explain the formula for calculating cable forces, provide a real-life example, and uncover some interesting facts along the way.

Force in Cable at the Support Ends Calculator
Midspan Force in Cable N
Unit Load N/m
Cable Span m
Cable Force Calculator Results
Force at Support = N
Learn about the Cable Force Calculator, its formula, real-life applications, and interesting facts in this engineering tutorial.

1. Understanding Cable Forces

Cable forces refer to the tension or pulling forces experienced by cables or wires that are used to support loads or transmit forces. Cables are widely used in engineering systems due to their high tensile strength and ability to withstand dynamic loads. They provide support, stability, and safety to structures and equipment.

Interesting fact: The concept of using cables in engineering dates back thousands of years. Ancient civilizations, such as the Egyptians and the Romans, employed ropes and cables made from natural fibers or animal tendons to construct suspension bridges and hoisting mechanisms.

2. The Formula

The formula for calculating cable forces depends on the specific situation and geometry of the cable system. However, a common formula used to estimate cable tension is based on the equilibrium of forces. It can be expressed as:

T = (W * L) / (2 * sin(θ))


  • T is the cable tension or force in Newtons (N)
  • W is the total load or weight being supported by the cable in Newtons (N)
  • L is the horizontal span or length of the cable in meters (m)
  • θ is the angle between the cable and the horizontal plane in degrees (°)

This formula calculates the cable tension by considering the weight being supported and the geometry of the cable system. The angle θ represents the inclination or sag of the cable, which affects the distribution of forces along the cable.

3. Real-Life Application

To illustrate the practical application of the cable force calculator, let's consider the construction of a suspension bridge. Suspension bridges rely on cables to support the weight of the bridge deck and distribute the loads to the bridge towers or anchorages.

For example, suppose we have a suspension bridge with a horizontal span (L) of 500 meters and a total weight (W) of 10,000,000 Newtons (approximately $1,000,000). Assuming the cables have an inclination angle (θ) of 5 degrees, we can use the formula to estimate the cable tension:

T = (10,000,000 N * 500 m) / (2 * sin(5°))

After performing the calculation, we find that the estimated cable tension is approximately 1,140,285 Newtons. This information is crucial for engineers to design the cable system, select appropriate cable materials, and ensure the structural integrity and safety of the suspension bridge.

4. Interesting Facts

Now let's uncover some interesting facts about cable forces:

  1. Cable Elasticity: Cables are not perfectly rigid and exhibit some degree of elasticity. When subjected to tension forces, they elongate slightly, known as cable stretch. This phenomenon is an important consideration in engineering design, especially for long-span cable systems such as suspension bridges, where the elongation of cables can affect their performance and stability.
  2. Cable Damping: Cables also possess damping characteristics, meaning they can absorb and dissipate energy when subjected to dynamic loads or vibrations. This damping property is advantageous in engineering applications where it helps reduce the amplitude of oscillations and mitigate the effects of wind-induced vibrations in cable-supported structures.
  3. Prestressed Cables: In certain applications, cables are intentionally preloaded or prestressed to counteract external loads and increase the structural efficiency of a system. Prestressing helps reduce cable sag, improves overall stability, and increases the load-carrying capacity of the structure. Prestressed cables are commonly used in bridge construction, high-rise buildings, and even in precast concrete components.
  4. Safety Factors: In engineering design, safety factors are applied to cable forces to ensure that the cables can withstand unexpected loads, variations in environmental conditions, and potential deterioration over time. Safety factors consider factors such as material properties, construction tolerances, and the uncertainty of load estimates to provide an additional margin of safety in the cable system.
  5. Multiple Cable Systems: Cable systems are often designed with multiple cables arranged in specific configurations. The use of multiple cables provides redundancy, enhances stability, and distributes the load more evenly across the structure. Examples of multiple cable systems include cable-stayed bridges, cable-net structures, and suspension roofs.

These interesting facts highlight the significance of cable forces in engineering applications and the complexities involved in designing and analyzing cable systems.


In this tutorial, we explored the concept of cable forces and their calculator. Cable forces are critical in various engineering fields, particularly in applications involving suspension bridges, cable-stayed structures, and other cable-supported systems. The formula for calculating cable tension provided a useful tool for engineers to estimate and analyze cable forces.

By understanding cable forces and utilizing the cable force calculator, engineers can design structures and systems that ensure safe and reliable performance. The knowledge of cable forces allows for accurate determination of cable properties, selection of appropriate materials, and optimization of the overall structural design.

Remember, cable forces are fundamental to the stability, strength, and load-carrying capacity of cable-supported structures. The study of cable systems continues to evolve, with ongoing research and advancements aimed at improving efficiency, durability, and safety in engineering applications.