A polymath, also known colloquially as a Renaissance man, is someone who has significant knowledge and expertise in several different, diverse subject areas. The Internet has brought almost limitless information to people around the world, making becoming a polymath easier than ever. However, at the same time the need for polymaths has dwindled as the key to success in many industries and businesses is finding a niche, or one specific area of expertise.
Brainstorm about which fields of study you wish to explore on your way to becoming a polymath. Pursing what interests you would be a good idea. Ideally, the fields should be diverse. If you became an expert in medicine and biology, two closely related fields, people might dispute your polymath status. Ideally, you should plan to become an expert in at least three different fields. If you are already an expert in a field, or are on your way to becoming one, this will reduce the amount of work needed to become a polymath.
Estimate how much time you have each day to devote to study and practice for your quest to become a polymath. Experts in a given field put in an average of 10,000 hours of practice or study to achieve their expert status, so you should plan to put in 30,000 hours to become an expert in three different fields.
Divide 30,000 by the number of hours you have available to you each day to devote to being a polymath. Assuming you devote that amount of hours each day that you study, the number you get is how many days it will take to become a polymath.
Divide the total number of days by 365 if you plan to study and practice every day of the week, or 261 if you plan to take weekends off, to get the number of years it will take you to achieve your goal. If the number of years is greater than the average American life expectancy, which was 78.7 years in 2009, minus your age, then it likely will take too long to become a polymath. In which case, you need to rethink how many hours a day you can devote to achieving your polymath goal.
Decide whether you want to study all fields of interest at once, or if you want to tackle one at a time. Also form a rough plan for how you will study each field. For example, if you plan to study biology, then plan to start with introductory texts, perhaps high school or early college textbooks, and advance from there.
Begin studying and practicing each day, accessing whatever educational resources, such as schools, libraries, and the internet, are at your disposal.