To find the distance between two points on a number line, you use the formula:
\[ \text{Distance} = |a - b| \]
where \(a\) and \(b\) are the two points. In this case, \(a = -8\) and \(b = 16\).
Now, substituting the values:
\[ \text{Distance} = |-8 - 16| = |-24| = 24 \]
Thus, the distance between \(-8\) and \(16\) on a number line is \(24\).