expression
if you think about it; come to think of it
Used as a set phrase to introduce a realization or reconsideration, often at the beginning of a sentence.
考えてみれば、彼の言う通りかもしれない。
Come to think of it, he might be right.
考えてみれば、あの時が最後だった。
If I think about it now, that was the last time.
Similar meaning, but 考えてみれば often implies a stronger sense of realization or a hypothetical angle ('if you think about it'), while 考えてみると is more neutral ('when you think about it').
From 考える (to think) in the te-form + みる (to try) in the conditional form みれば, literally 'if one tries thinking about it'.