--- title: "BIST 50: Methodology" description: "BIST 50 is maintained by Borsa Istanbul and covers Turkish mid-large cap equity benchmark. How it selects and weights its constituents, and what it measures." canonical: https://www.getswoopr.com/stocks/indexes/bist-50/ source: "Swoopr Investment: https://www.getswoopr.com" --- # BIST 50: What It Measures and How It Is Built ## Direct Answer > The BIST 50 is a rule-based measurement of Turkish mid-large cap equity benchmark, maintained by Borsa Istanbul. 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 BIST 50 covers Turkish mid-large cap equity benchmark, within the Turkey market. Borsa Istanbul 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 Weighted by free float market value: number of shares times price times free float ratio times a weighting factor. Calculated in lira, dollars and euros as price and return versions, with no capping ratio listed for the headline BIST 50. 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 50 stocks of companies traded on the Stars Market that automatically include the BIST 30 stocks. The pool holds stocks that have traded at least 60 days, ranked by average free float market value and by daily average traded value, with the two ranks combined. Investment trusts and Watchlist Market stocks are excluded from all indices. 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. ## How long a listing must exist first A stock needs at least 60 days of trading to join the selection pool. A large IPO whose market value at the end of the offering exceeds one twentieth of the free float market value of BIST 30 joins from the fifth trading day in place of the smallest member. A seasoning rule is why a large new listing does not appear in an index the week it starts trading. It is a deliberate lag, and it means an index can under-represent a fast-growing part of the market for months at a time. ## When the membership is revised Reviewed quarterly on the last day of November, February, May and August, with new index periods starting in January, April, July and October and announced at least 10 days before. Three substitute stocks are named at each review. 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 BIST 50 is nested: it always contains the BIST 30, and the 20 stocks in the BIST 50 but not in the BIST 30 are published as the BIST 50 30 index. Entry needs rank 45 or better and exit only below rank 55. ## References - [Borsa Istanbul: Borsa Istanbul, BIST Market Cap Weighted Stock Indices Methodology, September 2026 edition](https://borsaistanbul.com/files/bist-mcw-equity-indices-m-eng-202609-clean.pdf), as published 2026. Every rule described on this page is taken from this document. ## Current BIST 50 constituents Borsa Istanbul publishes and licenses the BIST 50 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights. [Borsa Istanbul: official BIST 50 page](https://www.borsaistanbul.com/en/sayfa/2316/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 BIST 50? Borsa Istanbul maintains the BIST 50 and publishes the methodology document that defines its eligibility and weighting rules. ### What does the BIST 50 measure? It measures Turkish mid-large cap equity benchmark. 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 BIST 50 constituents? Borsa Istanbul 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.