By default, the returned value from a calculation is hidden from the user. You can make the question visible, if you'd like.
To do this, head to the question's configuration page and toggle off "Hide this question." You can then optionally configure conditional logic if you only want the field to be visible depending on answers to other questions.
The actual calculation itself is never shown to the user. Rather, only the returned value is shown if you make the question visible.
For example, if your calculation was
1 + 1, the user would only see
2, not the expression
1 + 1.