The processing time of your application depends on the type of application and also the processing center. Here is an example of current processing times at the Tampa USCIS office:
- Naturalization (N-400): 9-13 months
- Certificate of Citizenship (N-600): 6.5-16 months
- Citizenship and Issuance of Certificate Under Section 322 (N-600K): 6.5-25.5 months
A thing to note about processing times is that you will see the times as a range, as given above, or the standard format depending on your form type. The USCIS is testing the time range method for the three forms given above and many other forms (form names are available here).
The first figure given in the range is the months for processing half of the cases. The second figure is the months for processing 93% of the cases. For forms that are not part of the test, the agency provides an upper limit of 130% of the processing time.
You can find the time for your case from the following USCIS page. This section of the site also gives you other useful information, including what to do if your case is taking more time than normal to process.