how long is a piece of string?

成語所屬單字long

how long is a piece of string? — 慣用語

1. Used to say that there is no definite answer to a question.

1.慣用語
釋義

沒有確切答案

Used to say that there is no definite answer to a question.

例句

When asked how long the project would take, he replied, 'How long is a piece of string?'

How long is a piece of string? It depends on many factors.