失之毫釐，差之千里 [－－－厘－－－－－]

Jyutping sat1 zi1 hou4 lei4 , caa1 zi1 cin1 lei5
Pinyin shī zhī háo lí , chà zhī qiān lǐ

Definitions (CC-CEDICT)
  1. a tiny lapse can lead to a huge mistake (idiom); a minor discrepancy leading to enormous losses