I'd better be off is a gentle way of saying you must leave. Right, I'd better be off.
The better makes it sound like an obligation rather than a choice, which is the politeness of it. It gives the other person a moment to protest before you stand up.
1phrasei'd better be offA gentle way of saying you must leave.
“He looked at the clock and said I'd better be off.”
i'd better be off is a phrase.
Practised in Small Talk & Everyday Phrases