How to Report Pearson's r (Pearson's Correlation Coefficient) in APA Style
The APA has precise requirements for reporting the results of statistical tests, which means as well as getting the basic format right, you need to pay attention to the placing of brackets, punctuation, italics, and so on.
Happily, the basic format for citing Pearson's r is not too complex, as you can see here (the color red means you substitute in the appropriate value from your study).
r(degress of freedom) = the r statistic, p = p value.
Example
Imagine we have conducted a study of 40 students that looked at whether IQ scores and GPA are correlated. We might report the results like this:
IQ and GPA were found to be moderately positively correlated, r(38) = .34, p = .032.
Other Examples
The variables shoe size and height were found to be strongly correlated, r(128) = .89, p < .01.
Among the students of Hogwarts University, the number of hours playing Fortnite per week and midterm exam results were negatively correlated, r(78) = -.45, p < .001.
Notes
Here are some things you should watch out for.
1. There are two ways to report p values. The first way is to cite the alpha value as in the second example above. The second way, very much the preferred way in the age of computer aided calculations (and the way recommended by the APA), is to report the exact p value (as in our main example). If you report the exact p value, then you need to state your alpha level early in your results section. The other thing to note here is that if your p value is less than .001, it's conventional simply to state p < .001, rather than give the exact value.
2. The r statistic should be stated at 2 decimal places.
3. Remember to drop the leading 0 from both r and the p value (i.e., not 0.34, but rather .34).
4. You don't need to provide the formula for r.
5. Degrees of freedom for r is N - 2 (the number of data points minus 2).