--- title: "IBrX 100: Methodology" description: "IBrX 100 is maintained by B3 and covers top 100 most traded companies on B3 by trading value and number of transactions. How it weights its constituents." canonical: https://www.getswoopr.com/stocks/indexes/ibrx-100/ source: "Swoopr Investment: https://www.getswoopr.com" --- # IBrX 100: What It Measures and How It Is Built ## Direct Answer > The IBrX 100 is a rule-based measurement of top 100 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 100 covers top 100 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 100 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 100 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 100 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 100 (IBrX 100 B3) index methodology page](https://www.b3.com.br/pt_br/market-data-e-indices/indices/indices-amplos/indice-brasil-100-ibrx-100-b3.htm), as published 2026. Every rule described on this page is taken from this document. ## Current IBrX 100 constituents B3 publishes and licenses the IBrX 100 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights. [B3: official IBrX 100 page](https://www.b3.com.br/en_us/market-data-and-indices/indices/) ## Related reading - [All stock market indexes](https://www.getswoopr.com/stocks/indexes/): how indexes are built, weighted and revised. - [Emerging Markets indexes](https://www.getswoopr.com/stocks/indexes/emerging-markets/): others covering the same region. - [Index concentration](https://www.getswoopr.com/technical-analysis/market-concentration/index-concentration/): measuring how much of an index sits in its largest holdings. - [Index rebalancing and inclusion effects](https://www.getswoopr.com/stocks/corporate-actions-catalysts/index-rebalancing-and-inclusion-effects/): what happens to a stock when index membership changes. ## Frequently Asked Questions ### Who maintains the IBrX 100? B3 maintains the IBrX 100 and publishes the methodology document that defines its eligibility and weighting rules. ### What does the IBrX 100 measure? It measures top 100 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 100 constituents? B3 publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence. ## About the author The [Swoopr Editorial Team](https://www.getswoopr.com/authors/swoopr-editorial-team/) writes Swoopr Investment's educational library, covering market structure, analysis methods and the mechanics behind the numbers investors read every day. Our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/) set out how this content is produced, reviewed and fixed when it is wrong.