His guess was square on.
square on
idiomaccurately, correctly.
The mechanic hit the problem square on when he said the engine needed a new part.
Her analysis of the political situation was square on, capturing the underlying tensions that others had failed to notice.
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back to square one
Located back at the start, as after a dead end or failure.
- 02
square away
To finish, complete, tidy or put in order.
- 03
square meal
A (nutritionally) complete and satisfying meal, especially one suitable for a person performing physical labour.
- 04
square one
The place where one begins; a lack of progress.
- 05
square peg in a round hole
Someone or something that does not fit well or at all in a certain setting; a misfit; hence, someone or something that will not succeed in an endeavour, except possibly with much effort and force.
- 06
square shooter
A person who is fair, trustworthy, or forthright; a person who bargains or transacts business in a fair, honest manner.