The BUMIX is a stock market index composed of 12 to 25 small and medium-sized companies listed on Budapest Stock Exchange.^[1]

BUMIX operates (similarly to BUX), as a total return index, i.e., the dividend payout also plays a role in its performance evaluation.^{[citation needed]} Only those series of shares can be admitted to the BUMIX basket where the market capitalisation adjusted for free float does not exceed HUF 125 billion. The calculation method, the review, and the handling of corporate actions is the same as the process applied in the case of the BUX index.

The index is based on prices generated in the electronic trading system Xetra.^{[citation needed]}