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Unrounded Equal-Class Width

Divide a numerical range into equal-width classes, retaining the unrounded width and compatible inverse values.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A range from 10 to 30 divided into four equal classes has unrounded class width (30 − 10)/4 = 5.

Equal class width = (maximum − minimum) / number of classes

Worked example

Enter these known values and leave the other values blank.

Lower range boundary
10
Upper range boundary
30
Whole number of classes
4
Unrounded class width
5

Assumptions and limitations

  • The upper boundary is greater than the lower boundary. Class count is a positive integer and width is positive.
  • This is the continuous range divided by the class count. It does not round up, add one for inclusive integer data or choose an optimal bin count.
  • Choose boundary inclusion rules when building a frequency table so each observation belongs to exactly one class.

Common questions

Should I round the result up?

That depends on your binning convention. This calculator keeps the exact unrounded model value so you can choose practical boundaries separately.

Does this choose a good number of histogram bins?

No. Supply the class count; a bin-selection rule would also need information about the dataset.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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