Frequency Distribution Calculator

How it is calculated

values is a list of numbers separated by spaces or commas (decimals use a dot) and classes is how many equal-width classes you want: a whole number from 1 to 1000. A fractional class count such as 2.5 shows no result.

range = max − min
width = range ÷ classes, rounded up to a whole number when every value is a whole number
class index = floor((value − min) ÷ width)

Class 1 starts at the minimum, and each class takes values from its start up to, but not including, the start of the next. The largest value always goes in the last class. The result is one count per class plus the width, range, minimum and maximum. Decimal data keeps its exact width (0.8 ÷ 4 = 0.2). If all values are equal, any item is not a number, or the list is empty, there is no result.

Common mistakes

• Expecting the tool to print class boundaries. It reports only the counts and the width, so work the boundaries out yourself: start at the minimum and add the width each time.
• Entering decimals with a comma, such as 2,5. A comma is a separator, so it reads as the two values 2 and 5; always use a dot.
• Entering a fractional or zero number of classes. The class count must be a whole number of at least 1, otherwise there is no result.
• Thinking the last class ends exactly at the maximum. With whole-number data the width is rounded up, so the final class can extend past the largest value and some classes can end up empty.
• Choosing too many classes for a small data set. With 15 values and 12 classes most classes hold one or none, and the pattern is lost.