Quiet-Quite | Commonly Confused Words

Quiet

/ˈkwaɪət/

Making little or no noise; having a calm or silent atmosphere

People say that you are the quietest man in Britain."You will not find a quieter man in all of England.Independently they quieted her doubt.

/kwaɪt/

To a considerable or significant extent, often emphasizing the degree or level of an adjective or situation

He's honest, you know, quite honest.O dear me, it seems quite a sin to drink it!''Quite true!' replied the Duchess.

Quiet is about silence, like quiet as a mouse. If you replace the e with m, you get quiet from silent.
Quite is about degree or extent, like quite a few. Think of the phrase being quite sure – it's about certainty, not silence.
The letter e at the end of quite makes it about extent, like extending a line.