ても～きれないCannot do enough, however much one does
This repeated-verb pattern says that however much an action is performed, it still cannot be completed or carried far enough. It works both for literal tasks and for strong emotional responses such as gratitude, apology, and regret.
How the pattern works
The first half presents the action as something that could be repeated or intensified without limit. The final きれない says that even then the action would not reach its endpoint or an adequate degree. Words meaning “however much,” such as いくら and どれほど, often make that unlimited scale explicit.
An emotional response
どれほどご支援に感謝しても、感謝しきれません。
I cannot thank you enough for your support.
AnalyzeThe gratitude is presented as so great that no amount of thanking could fully express it.
A literal task
倉庫の箱は、一日中数えても数えきれなかった。
The boxes in the warehouse were too numerous to finish counting, even after a full day.
AnalyzeChoose a scalable action
This pattern is most natural when the action has an endpoint or can be increased in degree. Counting, reading, checking, and handling can be completed or exhausted; gratitude, apology, regret, and praise can be expressed more or less fully. A verb with no sensible endpoint or scale will usually sound forced in this frame. Keep the final negative: changing きれない to きれる removes the meaning that the action remains insufficient.
Plain inability versus never enough
A plain form such as 数えきれない simply says that counting everything is impossible. The repeated frame 数えても数えきれない goes further: however much counting is done, it still will not be enough to reach the end.
More examples
今回ご迷惑をおかけしたことは、いくら謝っても謝りきれません。
No apology could ever be enough for the trouble caused this time.
Analyze私はあの日の判断を、どれほど悔やんでも悔やみきれない。
I can never regret the decision I made that day enough.
Analyzeこの美術館の収蔵品は、一日かけて見ても見きれない。
This museum has more items in its collection than one could possibly see in a day.
Analyze問い合わせが多く、全員で対応しても対応しきれません。
There are so many inquiries that even the whole team cannot handle them all.
Analyze私は集まった証言を一晩読んでも読みきれなかった。
Even after reading the collected testimony all night, I could not finish it.
Analyzeどれほど言葉を尽くして説明しても、説明しきれない部分がある。
There are parts that cannot be fully explained, however carefully one explains them.
Analyze