You need to know around 1,500 to 2,000 words to complete TOPIK 1. To be more precise, the TOPIK 1 exam includes two sub-levels : 1급 you'll need you to know how to express yourself in simple everyday conversations by making simple sentences from 800 basic words. 2급 includes discussion of familiar topics using about 1,500∼2,000 words, making sure you adapt your speech correctly to formal and informal situations.