せいぜい (seizei): At most or at best
～せいぜい (seizei)
Meaning
At most; at best; to the extent possible
Formation and usage
せいぜい + an amount or degree, usually an upper limit. A separate use before an action refers to doing as much as possible.
Explanation
Usually mark an upper limit in the speaker's estimate, suggesting no more than that. It can also refer to doing as much as possible. Advice with seizei may sound dismissive or sarcastic in some contexts, so use it carefully.
Examples
この箱に入る本は、せいぜい十冊です。
This box can hold ten books at most.
ここから駅までは、歩いてせいぜい十五分です。
The station is at most a fifteen-minute walk from here.
今日使えるお金は、せいぜい千円です。
I can spend no more than one thousand yen today.
一日に覚えられる単語は、せいぜい二十個です。
I can learn at most twenty words a day.
会場に残っていたのは、せいぜい五人でした。
There were no more than five people left at the venue.
How related patterns differ
に限る can recommend the best option or state a restriction. せいぜい marks an estimated upper limit. べき concerns what should be done, よりほかない means no alternative remains, and わけにはいかない concerns duties or principles.