Quick Answer. Any amount of hours that do not exceed 40 hours per week are considered part-time hours. Most companies consider the traditional part-time hours to be 20 to 37 1/2 hours per week. However, under the Obama administration, new part-time hours have been re-defined as 30 hours per week or more. This law is designed to deter small business owners from hiring more part-time workers, which actually costs the business more money, and to make sure that part-time workers get more work hours and more benefits from their employers.