The range of a set of data is the difference between the highest and lowest value. To find the range of a data set, then, simply identify the highest and lowest values, and then subtract the lowest from the highest.
As an example, let’s find the range of the following data set: 3, 6, 1, 9. The highest value is 9 and the lowest value is 1, so the range is calculated 9 − 1 = 8. The range is 8.
Finding the range becomes slightly more difficult (though not much) when the set includes negative values. Remember that two negatives make a positive, so subtracting a negative is the same as adding. Consider this data set: 12, -4, -7, 8. The highest value is 12, and the lowest value is -7. The range is calculated 12 − (-7) = 12 + 7 = 19. The range is 19.
One way to think of range is as the distance between the highest and lowest values on the number line. The highest number will be the farthest to the right, and the lowest value will be the farthest to the left. Also like a distance, range can never be negative. If all the values in the data set are the same, the range will be zero, but it will never be negative.