The figure he came up with was really just a shot in the dark.

他得出的数字实际上只是瞎猜而已。

《牛津词典》

In one shot, standing on a runway in the dark, Chávez points to a building where he was imprisoned during a coup and where some of his men lost their lives.

在一个镜头中，查韦斯站在黑暗中的跑道上，指着一座他在一次政变中被囚禁的建筑，他的一些手下在那里丧生。

youdao

We had nothing to go by. It was a shot in the dark, but it turned out right.

我们是没有根据的，只不过瞎猜，可是结果却猜对了。

《新英汉大辞典》

These are all issues on which a vote for Mr Romney is more of a shot in the dark than a vote to re-elect the president.

ECONOMIST: Conclusion

The company's lawyers had argued jury misconduct but, as the court didn't even allow a hearing on the subject, that seems to have been a bit of a shot in the dark.

ENGADGET: Editor's Letter: Looking back

Relying on our intuitions alone for self-knowledge is dangerous, because thanks to the nature of the adaptive unconscious, they are often no more accurate than a shot in the dark.

FORBES: Q: Who Knows You Best? A: It's Not You