adverb, noun which may take the genitive case particle 'no'
more than expected; beyond expectations
Used adverbially or with の to describe a result that exceeds what was anticipated. Often appears with verbs like なる, だ, or 難しい.
試験は予想以上に難しかった。
The exam was more difficult than expected.
予想以上の成果が出た。
We achieved results beyond expectations.
The exam was more difficult than I expected.
The new product got a bigger response than expected.
The construction took more time than expected.
予想外 emphasizes surprise at something unforeseen, while 予想以上 neutrally states that a result exceeded the expected level.
案外 expresses personal surprise that something turned out differently than thought, whereas 予想以上 specifically measures a result as exceeding a prior estimate.
Compound of 予想 (expectation) + 以上 (more than, above). The meaning is transparent from its parts.