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Catenary Calculator

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A Catenary Calculator is a tool that helps predict the shape of a hanging cable or chain when it is supported only at its ends. The shape formed by such a hanging chain or cable is known as a catenary curve, which looks like a gentle arch. This shape is important in physics and engineering, especially when designing structures like suspension bridges and power lines.

Purpose and Functionality

The main purpose of the Catenary Calculator is to help engineers and designers understand how a cable or chain will hang under its own weight. By inputting the distance between the supports (horizontal span) and the maximum sag (the lowest point of the curve), the calculator can determine the exact shape of the curve. This information is crucial for ensuring the stability and safety of structures that use cables or chains.

How It Works

The Catenary Calculator uses a mathematical formula to find the shape of the catenary curve. The general equation for a catenary curve is:



  • ๐‘ฆy is the vertical position of the curve at any point ๐‘ฅx,
  • ๐‘Ža is the catenary constant, representing the horizontal distance from the curve's lowest point to where the curve's slope is 1,
  • coshโกcosh is the hyperbolic cosine function.

Inputs for a Catenary Calculator

To use the calculator, you need to provide:

  • Horizontal Span (๐‘ฅx): The total horizontal distance between the two supports.
  • Sag (๐‘ s): The maximum vertical distance between the lowest point of the cable and the line drawn between the two supports.

Calculation Process

  1. Determine the Catenary Constant (๐‘Ža): ๐‘Ž=๐‘ coshโกโˆ’1(๐‘ฅ2๐‘ +1)a=coshโˆ’1(2sxโ€‹+1)sโ€‹ This formula helps find the value of ๐‘Ža using the known values of ๐‘ฅx (half of the horizontal span) and ๐‘ s (sag).
  2. Calculate the Position of the Catenary Curve: Once ๐‘Ža is known, you can find the vertical position ๐‘ฆy for any point along the horizontal span ๐‘ฅx using the catenary curve equation.

Step-by-Step Example

Let's see an example to understand how the Catenary Calculator works.


  • Horizontal Span (๐‘ฅx): 100 meters
  • Sag (๐‘ s): 10 meters


  1. Calculate the Catenary Constant (๐‘Ža): ๐‘Ž=10coshโกโˆ’1(100/210+1)โ‰ˆ15.81a=coshโˆ’1(10100/2โ€‹+1)10โ€‹โ‰ˆ15.81
  2. Calculate Positions Along the Curve:
    • For ๐‘ฅ=0x=0 (midpoint), ๐‘ฆ=15.81coshโก(0)=15.81ย metersy=15.81cosh(0)=15.81ย meters
    • For ๐‘ฅ=50x=50 meters, ๐‘ฆ=15.81coshโก(5015.81)y=15.81cosh(15.8150โ€‹)

These values provide the vertical positions of the cable at various points along the horizontal span, giving the shape of the curve.

Relevant Information Table

Horizontal Position (๐‘ฅx)Vertical Position (๐‘ฆy)
25y calculated at 25 meters
50y calculated at 50 meters
75y calculated at 75 meters
100y calculated at 100 meters


The Catenary Calculator is a valuable tool for engineers and designers working with hanging cables or chains. By inputting the horizontal span and sag, the calculator provides the catenary constant and the vertical positions along the curve. This information is essential for designing stable and safe structures like suspension bridges and power lines. The calculator simplifies complex mathematical calculations, making it easier to predict and plan for real-world applications.

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