Why do we count the initial number when we say something is X times bigger?

Question

Why do we count the initial number when we say something is X times bigger?

In: 42

Answer 1

The answer is simply “why not?”

There is inherent problem with it. To the contrary, if you want to calculate the new size, you just multiply the old size with the number before “times”. Otherwise you would first need to add 1 to the factor, or add the original size at the end, both extra effort.

And if you want to do it the other way, there even is already language for it: “larger by X times (it’s size)” or “smaller by Y percent”. This makes sense when you want to focus on the loss/gain/difference.

It would also be inconveniently weird for shrinking. Instead of “one third as large” or “1/3 times the size”, we would need to say/write “minus two thirds larger” or “larger by -2/3 times (its size)”. Negative numbers for no good reason, and definitely confusing.

Edit: clarity.