數字算錯
最直接的一支：算的是看得見的東西，時間、錢、份量、長度。
noun · B2
A mistake in working out a number or an amount — how long a job will take, how much money you will need, how much food or space there is, and so on.
算錯；估算錯誤
核心畫面
One way to hold this word: you worked something out in your head, and the answer came out wrong. Picture someone counting cups for a party and forgetting half the guests. The counting was real, the effort was real, and the number was still short. The word names that wrong answer, not the person who reached it. That is why it moves so easily from numbers to judgment, because both are answers you worked out and both can be short.
可以想成：你在腦中算了一遍，答案出來是錯的。畫面像是一個人為派對數杯子，漏掉了一半的客人。他真的有數，也真的有用心，…更多收起
可以想成：你在腦中算了一遍，答案出來是錯的。畫面像是一個人為派對數杯子，漏掉了一半的客人。他真的有數，也真的有用心，但數字就是不夠。這個字指的是那個錯掉的答案，不是算錯的那個人。也因為這樣，它從數字滑到判斷上完全不費力——兩邊都是你算出來的答案，兩邊都可能算少了。From the word’s history
The packet's source gives the make-up plainly: mis- plus calculation. Mis- is the prefix English uses for doing something wrongly, and calculation is the working-out itself, so the word is simply a working-out that went wrong.
來源把組成寫得很清楚：mis- 加上 calculation。mis- 是英文用來表示「做錯了」的字首，calculation 就是那個「算」的動作。所以整個字就是「算錯了的那一次計算」。
Wiktionary entry supplied in this packet (kaikki:3f6f69a190036ae4:1449203728:9394): 'From mis- + calculation.'
Two branches
情勢看錯
同樣是在腦中算了一遍，只是這次算的是情勢和別人的反應，沒有數字可以核對。
noun · B2
A wrong judgment about a situation: you worked out what was happening, or what people would do, and it turned out you had it wrong. No numbers need to be involved.
誤判