An uncertain quantity vitiates the act.

Explanation

Where the subject matter of an instrument — the quantity conveyed, the sum promised, the obligation undertaken — is left uncertain, the act is void; the law requires that what is done be done with sufficient definiteness to be enforceable. (Duplicate maxim — see also 1.5.96.)

Where this applies

• The contract doesn't specify the quantity so the agreement may be void.
• An uncertain amount or quantity in a legal instrument makes the whole act void.
• The deal can't be enforced because nobody knows exactly what's being promised.

See also

• 1.5.96 An uncertain quantity vitiates the act.