The distance between two points on a number line can be calculated using the formula:
\[ \text{Distance} = |a - b| \]
Where \(a\) and \(b\) are the two points. In this case, the points are \(-8\) and \(16\).
Substituting the values into the formula:
\[ \text{Distance} = |-8 - 16| = |-24| = 24 \]
Therefore, the distance between \(-8\) and \(16\) on a number line is \(24\).