Cantilever Beam Calculator

Calculate the stiffness (k) in a cantilever beam using Young's Modulus, area moment of inertia and varying beam lengths.

Cantilever Beam Calculator
Young's Modulus (E) Nm-2
Area Moment of Inertia (I) m4
Length (l) m
Cantilever Beam Calculator Results
Stiffness (k) = Nm-1

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Calculate the stiffness (k) in a cantilever beam using Young's Modulus, area moment of inertia and varying beam lengths.

Note on Young's modulus

In solid mechanics, Young's modulus (E) is a measure of the stiffness of an isotropic elastic material. It is also known as the Young modulus, modulus of elasticity, elastic modulus (though Young's modulus is actually one of several elastic moduli such as the bulk modulus and the shear modulus) or tensile modulus. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds.[1] This can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material.

Young's modulus is named after Thomas Young, the 19th century British scientist. However, the concept was developed in 1727 by Leonhard Euler, and the first experiments that used the concept of Young's modulus in its current form were performed by the Italian scientist Giordano Riccati in 1782 - predating Young's work by 25 years.

Welcome to this engineering tutorial where we will explore the fascinating world of cantilever beams and their calculator. Cantilever beams are a common structural element used in various engineering applications, including buildings, bridges, and support structures. In this tutorial, we will discuss the topic, explain the formula for calculating the deflection and stress in a cantilever beam, provide a real-life example, and uncover some interesting facts along the way.

1. Understanding Cantilever Beams

A cantilever beam is a type of structural element that is supported at only one end while the other end remains free. This configuration allows the beam to extend horizontally and support loads applied at its free end. Cantilever beams are known for their simplicity, versatility, and ability to span long distances without intermediate supports.

Interesting fact: Cantilever beams have been used in architectural and engineering marvels throughout history. Notable examples include the cantilever balconies of Frank Lloyd Wright's Fallingwater, the Forth Bridge in Scotland, and the iconic cantilever wings of aircraft like the Spitfire.

2. The Formula

The formula for calculating the deflection and stress in a cantilever beam depends on its geometry, material properties, and the applied load. Two common formulas used are:

Deflection: δ = (W * L3) / (3 * E * I)

Stress: σ = (M * y) / I


  • δ is the deflection of the cantilever beam in meters (m)
  • W is the applied load or force at the free end of the beam in Newtons (N)
  • L is the length of the cantilever beam in meters (m)
  • E is the modulus of elasticity of the material in Pascals (Pa)
  • I is the moment of inertia of the beam's cross-sectional shape in meters to the power of 4 (m4)
  • σ is the stress in the beam at a specific point in Pascals (Pa)
  • M is the bending moment at the point of interest in Newton-meters (Nm)
  • y is the perpendicular distance from the neutral axis to the point of interest in meters (m)

These formulas allow engineers to determine the deflection and stress experienced by a cantilever beam under a given load. The deflection formula considers the applied load, beam length, material properties, and the moment of inertia of the beam's cross-sectional shape. The stress formula considers the bending moment, perpendicular distance from the neutral axis, and the moment of inertia.

3. Real-Life Application

To illustrate the practical application of the Cantilever Beam Calculator, let's consider a real-life example of a cantilever beam used in construction. Imagine designing a cantilevered balcony for a high-rise building.

Suppose we have a cantilevered balcony with a length (L) of 4 meters and a cross-sectional shape with a moment of inertia (I) of 0.1 m4. The balcony is intended to support a uniformly distributed load of 5000 N (approximately $500) per meter. Using the formulas, we can calculate the deflection and stress at a specific point on the balcony.

For the deflection calculation:

δ = (W * L3) / (3 * E * I)

Substituting the values:

δ = (5000 N/m * (4 m)3) / (3 * E * 0.1 m4)

Assuming a typical modulus of elasticity for a construction material, such as steel, of 200 GPa (200 x 10^9 Pa), we can calculate the deflection:

δ = (5000 N/m * 64 m3) / (3 * 200 x 10^9 Pa * 0.1 m4)

After performing the calculation, we find that the deflection of the cantilevered balcony is approximately 0.00005 meters (or 0.05 mm).

For the stress calculation:

σ = (M * y) / I

Assuming a uniformly distributed load, the maximum bending moment occurs at the fixed support. At that location, the bending moment can be calculated as:

M = (W * L) / 4

Substituting the values:

M = (5000 N/m * 4 m) / 4

So, the bending moment is 5000 Nm (or 5000 Nm/m).

Assuming the balcony has a rectangular cross-sectional shape, the neutral axis is located at the centroid, which is at half the height of the shape. Thus, assuming a height of 0.3 meters, the perpendicular distance (y) from the neutral axis to the point of interest can be calculated as half the height:

y = 0.3 m / 2

Therefore, y is equal to 0.15 meters.

Substituting the values into the stress formula:

σ = (5000 Nm * 0.15 m) / 0.1 m4

After performing the calculation, we find that the stress at the point of interest is 75000 Pa (or 75 kPa).

4. Interesting Facts

Now let's uncover some interesting facts about cantilever beams:

  1. Stability and Structural Integrity: Cantilever beams rely on the strength and stability of their fixed support to resist bending and support loads. Proper design, material selection, and consideration of load distribution are crucial to ensuring the structural integrity and safety of cantilevered structures.
  2. Use in Architecture: Cantilever beams are commonly used in architectural designs to create visually striking overhangs, balconies, and roof structures. Their unique aesthetic appeal and ability to create open, spacious areas without the need for additional supports make them popular in modern architectural designs.
  3. Challenges of Long Spans: Cantilever beams with long spans present engineering challenges. The longer the span, the higher the deflection and stress experienced by the beam. Structural engineers must carefully consider the material properties, cross-sectional shape, and loading conditions to ensure that the beam can safely support the desired loads and meet deflection limits.
  4. Dynamic Effects: Dynamic loads, such as wind or seismic forces, can significantly impact the behavior of cantilever beams. Dynamic analysis techniques, such as modal analysis and wind tunnel testing, are employed to assess the response of cantilevered structures under dynamic conditions and ensure their stability and safety.
  5. Advancements in Materials: Modern engineering has seen advancements in materials used for cantilever beams. High-strength materials, such as steel alloys and composite materials, offer increased strength-to-weight ratios, allowing for longer and more efficient cantilever designs. These materials also provide enhanced resistance to corrosion, fatigue, and other environmental factors.
  6. Applications Beyond Structures: Cantilever beam principles are not limited to structural engineering. They are also applied in other fields, such as micro-electromechanical systems (MEMS), where cantilever beams are used in sensors, actuators, and resonators. The precise deflection and stress calculations are essential for optimizing the performance of these devices.


In this tutorial, we explored the fascinating world of cantilever beams and their calculator. Cantilever beams are versatile structural elements used in various engineering applications. The formulas for calculating deflection and stress provided engineers with valuable tools to analyze and design cantilevered structures.

By understanding the principles of cantilever beams and utilizing the Cantilever Beam Calculator, engineers can make informed decisions regarding material selection, cross-sectional shape, and loading conditions to ensure the safety and efficiency of their designs.

Remember, cantilever beams offer unique architectural possibilities and engineering solutions. They are widely used in both small-scale and large-scale structures, providing innovative design options and functional spaces. Through careful analysis and application of the cantilever beam principles, engineers continue to push the boundaries of what can be achieved in structural design and architectural expression.