add up phr v 1 [I,T add sth ↔ up] to put numbers or amounts together and then calculate the total （把数字）加起来〔以求得总数〕: Add your scores up and we'll see who won. 把你们的得分加起来，我们就知道谁赢了。 2 not add up to not seem true or reasonable 说不通，不合情理: His story just doesn't add up. 他的故事根本不合情理。