計 is one of the most commonly used Japanese kanji, and it also has a lot of special readings in addition to the standard onyomi and kunyomi readings.
ONYOMI 音読み
はか.る haka.ru はか.らう haka.rau
KUNYOMI 訓読み
ケイ kei
Examples
一年の計は元旦にあり。New Year’s Day is the key to the year.昭和天皇が靖国神社で75年までに戦後計8回参拝した。In the post-War period, up until 1975, Emperor Showa prayed at the Yasukuni Shrine a total of 8 times.産科・婦人科の計61床も満床で、受け入れは不可能と答えたという。They replied that because all 61 beds in the obstetrics/gynaecology department were full, no admissions were possible.