Warren Buffett has never detailed the process he uses to value the businesses he acquires for Berkshire Hathaway. However, over the years, he has provided some limited insight into his methods.
Q3 2020 hedge fund letters, conferences and more
Based on these comments, it is widely assumed that Buffett uses a discount cash flow model to estimate the intrinsic value for a business. Although his right-hand man, Charlie Munger, has stated that he has never seen Buffett use one of these models, his comments suggest otherwise.

