You can do OPT for a cumulative maximum of 12 months during any uninterrupted stay in F-1 status. You may be authorized to do 12 months of OPT following each educational level, e.g., MA→PhD. For students who majored in STEM (Science, Technology, Engineering or Mathematics), there is an additional 17-month extension; however, MIIS majors to not qualify. There may also be an extension of OPT if you have an approved or receipted H-1b application. Ask the OIS for more information on this.