一诺千金的英文：
[Literal Meaning]
one/promise/thousand/gold
a promise worth one thousand taels of gold

[解释]
诺：许诺。许下的一个诺言有千金的价值。比喻说话算数，很有信用。

[Explanation]
to be sure to keep one's promise

[例子]
这个人我最了解了，他一诺千金，从来不会反悔。

[Example]
I know him the best. He is sure to keep his promise and never regrets.

[英文等价词]
true to one's word
a promise that will be kept

What you said is a promise which is as good as a thousand bars of gold.
你的话可是一诺千金。