add up phrasal verb ( see also ↑ add )
1 . to calculate the total of several numbers:
I can add up in my head quite easily.
add something ↔ up
Specialized software adds up the statistics.
2 . not add up
a) if a set of facts does not add up, it does not provide a reasonable explanation for a situation:
He was troubled by a feeling that things just didn’t add up.
b) if sums, numbers etc do not add up, there is a mistake in them:
These figures don’t add up.
3 . it all adds up informal used to say that lots of small amounts gradually make a large total:
There are five of us using the phone so it all adds up.