How it works
The average (arithmetic mean) is the sum of the numbers divided by how many there are. For 4, 8, 15, 16, 23 and 42 the sum is 108 and the count is 6, so the mean is 18.
The median (middle value when sorted) and mode (most frequent value) are shown too. When a list has a few extreme values, the median often describes a "typical" value better than the mean.
Formula
mean = (x₁ + x₂ + … + xₙ) ÷ n
Questions people ask
What is the difference between mean, median and mode?
The mean is the sum divided by the count. The median is the middle value of the sorted list (or the average of the two middle values). The mode is the value that appears most often.
How do I calculate a weighted average?
Multiply each value by its weight, add those products, and divide by the sum of the weights. A plain average treats every value as weight 1.
Does the average have to be one of the numbers?
No. The average of 1 and 2 is 1.5, which is not in the list.