noun which may take the genitive case particle 'no'
not factored in; unaccounted for; unplanned for
Describes something that was not included in a plan, calculation, or expectation. Often used with ～の or as a noun.
The transportation cost was an unplanned expense.
His reaction was unexpected.
想定外 means 'beyond assumptions' or 'unforeseen', often used in formal contexts like disaster planning. 計算外 is more about personal plans or calculations.
Compound of 計算 (calculation) and 外 (outside). Literally 'outside the calculation'.