Unexpectedly; surprisingly — used to indicate that something is different from what was expected (more or less than anticipated).
試験は思いのほか簡単だった。
The exam was easier than I expected.
今日は思いのほか暖かいので、コートはいらないかもしれない。
It's surprisingly warm today, so I might not need a coat.
彼の日本語は思いのほか上手だ。
His Japanese is surprisingly good.
費用は思いのほかかからなかった。
It didn't cost as much as I had expected.