Definition from Wiktionary, the free dictionary
- (transitive) To take a sum.
- Add up the prices and find out how much it will cost.
- (intransitive) To accumulate; to amount to.
- If you can save even a couple of dollars per day, it will add up to a lot over a year.
- (idiomatic, intransitive) To make sense; to be reasonable or consistent.
- His story just doesn't add up. Why would he have been at the restaurant the day before the event?
take a sum
be reasonable or consistent — see make sense