Add to something—increase or enhance something.
- It’s an old building so you get creaky sounds of the old building but I guess it adds to its rustic charm.
Add up to something—
1. (of values) give as a result, when joined.
- The bombing from B-52 stratofortresses ultimately added up to 800,000 tons of bombs.
2. amount to something; signify something.
- All that this adds up to is that you don’t want to help, so why not say so at once?