Direct Answer
The IBrX 50 is a rule-based measurement of top 50 most traded companies on B3 by trading value and number of transactions, maintained by B3. Like every index it owns nothing: it is a number produced by applying a published weighting formula to a selected list of companies, revised on a schedule the provider sets.
What this index covers
The IBrX 50 covers top 50 most traded companies on B3 by trading value and number of transactions, within the Brazil market. B3 defines which securities are eligible, how they are selected from that pool, and how much each one contributes to the published number.
The name states a target of 50 companies. A target is not a guarantee of the exact count on any given day: corporate actions, dual share classes and pending additions all move the real number around it.
How constituents are weighted
Constituents are weighted by free float market value.
The weighting method is the single biggest driver of how an index behaves. Two indexes covering the same market can diverge for years purely because they weight differently, which is why comparing index levels without knowing the method tells you very little.
What qualifies for inclusion
The universe is shares and units representing shares of B3 listed companies. An asset must rank in the top 50 by tradability ratio (IN), with a 90 percent buffer, trade in 95 percent of sessions, and not be a penny stock. BDRs and assets of companies in judicial or extrajudicial recovery, administration, intervention or other special listing situations are excluded.
Eligibility rules are the part of an index most readers never look at and the part that decides what it can possibly measure. A screen that excludes a whole sector, or admits only one listing venue, shapes the result far more than any day of trading does.
When the membership is revised
The index is rebalanced every four months. Each new portfolio starts on the first Monday of January, May and September.
Reconstitution is the one date an index changes shape by design rather than by price. Funds tracking it have to trade toward the new membership, which is why the schedule matters to anyone holding the tracker rather than only to the provider.
The rule that surprises people
The cut is a fixed count of 50 assets ranked by tradability, not by company size, so the index measures the most traded assets rather than the largest companies.
References
- B3: B3 Indice Brasil 50 (IBrX 50 B3) index methodology page, as published 2026. Every rule described on this page is taken from this document.
Current IBrX 50 constituents
B3 publishes and licenses the IBrX 50 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.
Related reading
- All stock market indexes: how indexes are built, weighted and revised.
- Emerging Markets indexes: others covering the same region.
- Index concentration: measuring how much of an index sits in its largest holdings.
- Index rebalancing and inclusion effects: what happens to a stock when index membership changes.
Frequently Asked Questions
Who maintains the IBrX 50?
B3 maintains the IBrX 50 and publishes the methodology document that defines its eligibility and weighting rules.
What does the IBrX 50 measure?
It measures top 50 most traded companies on B3 by trading value and number of transactions. The index is a calculated number applying a weighting formula to a selected list of companies, and it holds nothing itself.
Where can I see the current IBrX 50 constituents?
B3 publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence.