Usage

Almost.

I am short a quarter.

Thanks Micawber.. Is it informal, and used only in speech?

Or, we can use that in writing also? I am surprised that there is no preposition there..

It would normally appear informally, I imagine, but I think 'to be short' could be used anywhere.

However, to clarify:

A: I am a little short of money, so I can't buy this book.
B: How short are you?
A: I'm short (by) $2.00.

'Short of' indicates the material from which some quantity is deficient.
'Short (by) indicates the quantity deficient.

Thank you.

So, 'by' is optional is what you mean?

So we can say, "I am short by a quarter"?

Correct.

Thank you.