Formal:
* Miscalculation: A mistake made due to incorrect calculations or estimations.
* Misjudgment: A mistake made due to poor understanding or assessment of a situation.
* Error: A mistake, generally used in a more neutral context.
* Faux pas: A social blunder or mistake.
Informal:
* Fumble: To make a clumsy mistake, often with something physical.
* Slip-up: A minor mistake.
* Boo-boo: A childish term for a mistake, often used humorously.
* Goof: A silly mistake.
* Screw-up: A serious mistake.
* Botch: To do something badly or incompetently.
The best synonym to use depends on the context and the severity of the blunder.