Class Width Calculator

Created by Rahul Dhari
Reviewed by Hanna Pamuła, PhD and Jack Bowater
Last updated: Nov 19, 2022

The class width calculator can be utilized to find the class width of your data distribution. The class width formula works on the assumption that all classes are the same size. You can also use it to estimate the range of the data in a distribution. This tool also returns the class interval you should use for the given number of classes in your range. The tool also comes in handy if you want to present your distribution, like in a histogram. Continue reading to understand how to calculate class width.

🔎 If you want to learn more about data presentation, head to our histogram calculator.

What is class width?

The difference between the maximum and the minimum bounds of a distribution is called the class width, provided all the classes have the same width within the distribution. The class width can also be referred to as the difference between the lower limits of two consecutive classes. The calculator uses the class width formula to estimate this value, such that:

class width = (max - min) / n,

where:

  • max - Upper bound of a data set;
  • min - Lower bounds of a data set; and
  • n - Number of classes within the distribution.

How to use the class width calculator to find the class width?

Now that you know what is class width let's learn how to implement it. Follow the step-by-step instructions to obtain the class width for your data. Heads up! If you do not have the minimum and maximum values to find class width beforehand, you can use our minimum and maximum calculator.

  1. Use the maximum value of the distribution as the Maximum.

  2. Input the minimum value of the distribution as the Minimum.

  3. Enter the desired number of classes for the distribution as Number of classes.

  4. The calculator will now display the class width using the class width formula.

Example: How to calculate class width using the class width calculator

Consider the following marks on a test 15 students took: 45, 68, 82, 79, 67, 55, 75, 55, 85, 89, 90, 78, 45, 66, and 49.

  1. Identify the maximum and minimum values in the data set, which are 90 and 45, respectively.

  2. Enter the maximum and minimum values. The difference between the maximum and minimum values in a distribution, also called the range, is estimated by max - min = 45.

  3. Use the number of classes, say n = 9, to calculate class width i.e. class width = 45 / 9 = 5.

  4. The class width formula returns the appropriate class width to distribute this data into 9 classes, which is 5.

What to do with the class width parameter?

The class width, also known as the class interval, is crucial when it comes to representing data as a histogram. Once you know the appropriate class width, the range can be divided into several classes, which the size of each class equal to the class width. The end values for the class are known as the class limits. Every class has two limits - upper (or maximum) and lower (or minimum).

Arranging the data into its respective classes is useful when you want to find the frequency of occurrence of the values within the set. This data could be anything, be it marks scored by students, students' IQ levels, runs scored, or goals scored by your favorite players. Once you have the frequency of occurrence, you can use it to make a histogram. Here, the number of classes becomes the number of bars, and the difference or interval between the bar limits is your class width.

Explore our other tools to understand data distribution. We highly recommend Omni's mean median mode calculator to draw more conclusions about your distribution.

Rahul Dhari
Minimum
Maximum
Number of classes
Class width
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