Translation guide
Expresses that something is so obvious or well-known that it doesn't need to be stated. Japanese has several common set phrases for this, ranging from formal to casual.
To say that something is obvious and doesn't need to be mentioned.
The most direct and common equivalent. Literally 'there is no need to say'. Neutral to formal.
安全が第一であることは言うまでもない。
It goes without saying that safety comes first.
Adverbial form, used at the beginning of a sentence. 'Needless to say, ...'
言うまでもなく、健康は大切だ。
Needless to say, health is important.
Casual. 'It's obvious' or 'That's a given'. Often used in conversation.
彼が怒るのは当たり前だよ。
It goes without saying that he'd get angry.
Means 'of course'. Can be used to imply something is obvious, but is less emphatic than the set phrases.
Formal/literary. 'It is self-evident'. Used in academic or philosophical contexts.
その事実は自明だ。
That fact is self-evident.
言うまでもない is a set phrase suitable for both speech and writing, while 当たり前だ is more casual and direct. Use 言うまでもない in formal situations or when you want to sound polite.
彼の成功は言うまでもない。
His success goes without saying.
彼が成功するのは当たり前だ。
It's obvious he'll succeed.
もちろん、彼は来るよ。
Of course he's coming. (It goes without saying.)