How to Find Length of a Vector

The length (or magnitude) of a vector represents the size or amount of the vector irrespective of its direction. It gives you an idea of "how much" of the vector there is. The length is always a non-negative scalar value.

How to Find Length of a Vector

Step-by-step Guide to Find Length of a Vector

Here is a step-by-step guide to finding the length of a vector:

Step 1: Introduction – Vector Basics

A vector in the purest sense is a directional entity with both magnitude and direction. It can be visualized as an arrow pointing in a particular direction, the length of which signifies its magnitude.


  • Remember: The directionality of vectors differentiates them from scalar quantities, which only have magnitude.

Step 2: Mathematical Representation

For this guide, let’s focus on vectors in the Cartesian plane, especially:

  • \(2D\) vectors: Given as \(v = (x, y)\)
  • \(3D\) vectors: Given as \(v = (x, y, z)\)


  • Vector components, such as \(x\), \(y\), and \(z\), represent the vector’s projection on the respective axes.

Step 3: Graphic Visualization

Plot the vector on a graph (\(2D/3D\) as per vector dimensions). Imagine the vector as the hypotenuse of a right triangle in \(2D\) or the diagonal of a rectangular prism in \(3D\).


  • Visually, you can already gauge the length, but for exact measurements, mathematics comes into play!

Step 4: The Formula – Pythagorean Theorem

To determine the magnitude, the Pythagorean theorem is key:

  • For \(2D\): \(|v| = \sqrt{(x^2 + y^2)}\)
  • For \(3D\): \(|v| = \sqrt{(x^2 + y^2 + z^2})\)


  • For vectors beyond \(3D\), extend the formula: \(|v| = \sqrt{(x_1^2 + x_2^2 + … + x_n^2)}\) for \(n\)-dimensional space.

Step 5: Calculation Process

For 2D Vectors:

  1. Square each component: \(x^2\) and \(y^2\)
  2. Sum the squares: \(x^2 + y^2\)
  3. Find the square root of the sum to get the magnitude.

For 3D Vectors:

  1. Square each component: \(x^2, y^2\), and \(z^2\).
  2. Sum the squares: \(x^2 + y^2 + z^2\)
  3. Calculate the square root of the sum.


  • Precision is key! Ensure you use a calculator with enough decimal places if dealing with intricate vectors.

Step 6: Verification

Once you’ve determined the magnitude, it’s always a good practice to verify. Plot the vector and see if the calculated magnitude aligns with your visual interpretation.


  • Use software or graph plotting tools for an accurate representation.

Step 7: Beyond Basic Vectors

If you’re dealing with vectors in non-Cartesian coordinates (like polar, spherical, or cylindrical), you’d require coordinate transformations first before determining magnitude.


  • Study transformations keenly; they can become very handy in advanced physics and engineering tasks.

Step 8: Conclusion & Application

Understanding vector magnitude is foundational in fields like physics, engineering, computer graphics, and even in some advanced economic models. Whether you’re analyzing forces, velocities, or other vector quantities, knowing how to determine magnitude is quintessential!


  • Always seek real-world applications of your mathematical findings. This helps solidify understanding and appreciation.

With this structured and complex guide, you’re not just learning the process but also the intertwined intricacies of vectors in various dimensions and their relevance. Happy vector hunting!


Example 1:

Find the length of the vector \(b=(6,8)\).


To find the length (or magnitude) of a \(2D\) vector, we use the formula: \( ∣b∣\)\(=\sqrt {x^2+y^2}​\)

Where \(x\) and \(y\) are the components of the vector.

For vector \(b\):



Plug in the values:

\( ∣b∣\)\(=\sqrt{6^2+8^2​}\)

\( ∣b∣\)\(=\sqrt{36+64​}\)

\( ∣b∣\)\(=\sqrt{100}​\)

\( ∣b∣\)\(=10\)

So, the length of the vector \(b\) is \(10\).

Example 2:

Find the length of the vector \(e=(−3,9)\).


For a \(2D\) vector, the formula to find its length (or magnitude) is: \( ∣e∣\)\(=\sqrt{x^2+y^2}\)​

Where \(x\) and \(y\) represent the vector’s components.

Given vector \(e\):



Insert the values into the equation:

\( ∣e∣\)\(=\sqrt{(−3)^2+9^2​}\)

\( ∣e∣\)\(=\sqrt{9+81​}\)

\( ∣e∣\)\(=90​\)

The length of the vector \(e\) is \(90\)​. Simplifying further: \( ∣e∣\)\(=3\sqrt{10​}\) Which, when approximated to two decimal places, equals \(9.49\).

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