Find the highest value in the data
Find the lowest value in the data
Subtract the lowest value from the highest value to get the range
Decide the number of class intervals needed
Divide the range by the number of class intervals to get the class width
Round the class width to a convenient whole number if needed
Start the first class interval at or below the lowest value
Add the class width repeatedly to form the remaining class intervals
Ensure each class interval has no overlap with the next one
Ensure all data values are included in the intervals