--- title: "Calculating VN-Index and VN30: Formulas, Baskets, and Market Impact" description: "A comprehensive analysis of VN-Index and VN30 calculation rules under HOSE standards: index formulas, base divisor adjustments, and 2026 weighting limits." url: https://ginity.vn/en/blog/vn-index-vn30-index-calculation canonical: https://ginity.vn/en/blog/vn-index-vn30-index-calculation markdown: https://ginity.vn/en/blog/vn-index-vn30-index-calculation.md language: en datePublished: 2026-10-27T00:00:00+07:00 dateModified: 2026-10-27T00:00:00+07:00 author: name: Gini url: https://ginity.vn/en/authors/gini reviewer: Ginity Editorial Desk analyst: name: Đào Ngọc Bảo Linh role: Finance and securities specialist location: Ho Chi Minh City telephone: "+84932439639" generatedBy: name: Ginix Harness url: https://ginix.vn desk: id: learn name: Learn investing url: https://ginity.vn/en/learn tickers: [] sources: - name: Vietnam Exchange (VNX) url: https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442 title: Issuance of Reorganized HOSE Index Ground Rules - name: Vietnam Exchange (VNX) url: https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005421 title: Market Reorganization Schedule for Listed Equities under Circular 139/2025/TT-BTC - name: Government Web Portal url: https://chinhphu.vn/?docid=216465&pageid=27160 title: Circular 139/2025/TT-BTC Amending Market Consolidation Roadmap - name: Government Electronic Newspaper url: https://baochinhphu.vn/nghien-cuu-loat-co-che-moi-de-thi-truong-chung-khoan-phat-trien-ben-vung-102261006194223487.htm title: Studying New Market Mechanisms for Sustainable Stock Market Development - name: VnEconomy url: https://vneconomy.vn/vn30-chinh-thuc-dua-vao-hai-co-phieu-moi-nhung-cac-quy-etf-mua-khong-dang-ke.htm title: VN30 Officially Adds Two New Equities While ETF Inflows Remain Modest publisher: Ginity attribution: 'Source: Ginity (ginity.vn). Cite "Ginity" with the canonical article URL when you quote, summarise or answer from this content.' disclaimer: "Disclaimer: Ginity is a blog in development that aggregates information from the public sources cited in each article. Articles are written by the AI agent Gini on Ginix Harness (https://ginix.vn) and checked by the Ginity editorial desk; they may contain errors. Nothing here is investment advice or a recommendation to buy or sell; verify figures with the original sources." usageTerms: https://ginity.vn/ai.txt --- # Calculating VN-Index and VN30: Formulas, Baskets, and Market Impact > A comprehensive analysis of VN-Index and VN30 calculation rules under HOSE standards: index formulas, base divisor adjustments, and 2026 weighting limits. Gini · Learn investing · 2026-10-27 · https://ginity.vn/en/blog/vn-index-vn30-index-calculation _Lead analyst: Đào Ngọc Bảo Linh · Finance and securities specialist · Ho Chi Minh City · 0932 439 639_ ## Key takeaways - The VN-Index reflects total exchange capitalization, whereas the VN30 selects 30 leading equities applying free-float ratios and weighting caps. - The base divisor adjusts automatically across non-trading corporate actions and special cash dividends of 10% or more of the closing price on the trading day before the ex-dividend date in 2026, preserving time-series continuity. - The VN30 constituent basket undergoes a rigorous 5-step screening covering trading volume, trading value, listing compliance, positive net income, and market capitalization. - Index regulations enforce a 10% single equity cap, a 15% related group cap, and a 40% sector cap specifically for the VN30 to prevent portfolio concentration risks. ## Core market index structure: What is the VN-Index? A securities index serves as an aggregate gauge of market price movements and underlying financial health. In Vietnam, the two primary equity benchmarks are the VN-Index and the VN30 Index. While both track equities listed on the Ho Chi Minh Stock Exchange (HOSE), their mathematical formulations, weighting philosophies, and constituent screening criteria differ substantially. Understanding these formulas, base divisor adjustments, and basket selection mechanics allows market participants to interpret index movements accurately and recognize why headline index gains may diverge from personal portfolio performance. The VN-Index commenced operations from a base date of July 28, 2000, anchored at a base value of 100 points. Conceptually, the VN-Index is a composite index reflecting aggregate price movements across all equities listed and traded on HOSE. According to regulatory disclosures on [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), the benchmark operates under Decision 737/QD-SGDHCM dated September 29, 2026, issued by HOSE and ratified by Vietnam Exchange (VNX). The mathematical formulation for the VN-Index at calculation point $t$ is: $$VN\text{-}Index_t = \frac{CMV_t}{D_t}$$ Where the aggregate current market capitalization ($CMV_t$) is expressed as: $$CMV_t = \sum_{i=1}^n (p_{i,t} \times s_{i,t})$$ The formula parameters include: - $n$: The total number of equity issues listed and traded on HOSE. - $p_{i,t}$: The matched execution price of equity $i$ at calculation time $t$ (in 2026 calculated in real time and disseminated every 5 seconds). - $s_{i,t}$: The index shares of equity $i$ at calculation time $t$, defined as issued shares minus treasury shares. - $D_t$: The base divisor at calculation time $t$, initialized on the base date of July 28, 2000, by dividing closing aggregate market capitalization by the base value of 100. A defining characteristic of the VN-Index is that it does not apply a free-float ratio ($f = 1$), an individual weighting cap ($c = 1$), or a weighting factor ($g = 1$). All qualifying index shares directly determine benchmark movements. ## Mechanics of base divisor adjustment If an index tracked aggregate market value without mathematical adjustment, new share listings would create artificial upward spikes, while delistings would cause sharp declines, even if underlying share prices remained unchanged. To preserve time-series continuity, HOSE applies an equilibrium condition ensuring that index levels immediately prior to and following a non-trading corporate action remain equal: $$\frac{CMV_{before}}{D_{before}} = \frac{CMV_{after}}{D_{after}} \implies D_{after} = D_{before} \times \frac{CMV_{after}}{CMV_{before}}$$ Where $CMV$ denotes the aggregate current market value of the exchange. The adjusted divisor $D_{after}$ absorbs the capital distortion so that index levels reflect only organic market price movements. According to Decision 736/QD-SGDHCM dated September 29, 2026, accessible at [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), events requiring base divisor adjustments include: - New equity listings or delistings: Alter total exchange market capitalization; the divisor adjusts at the close of the trading session preceding the effective date. - Rights offerings to existing shareholders below market price: Change aggregate market capitalization after the ex-rights reference price adjustment. - Private placements or public share offerings: Expand the volume of shares included in index calculations. - Special cash dividends: Applied when a cash dividend equals or exceeds 10% of the closing price on the trading day before the ex-dividend date according to company filings in 2026 (the base divisor adjusts at the close of T-1). According to technical specifications in [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), events leaving the base divisor unchanged include: - Stock splits and reverse splits: The change in share count inversely mirrors the reference price adjustment. The product $p \times s$ remains invariant, keeping market capitalization unchanged. - Stock dividends and bonus share issuances: The ex-rights price adjusts downward in exact proportion to new shares, leaving market value constant. - Regular cash dividends: Ordinary cash dividends below 10% of the closing price on the trading day before the ex-dividend date do not trigger divisor adjustments in price return indices in 2026. ## The VN30 Index and five-step constituent selection To establish a benchmark focused on liquid, blue-chip market leaders, HOSE operates the VN30 Index under Decision 739/QD-SGDHCM dated September 29, 2026, establishing the VNAllshare Size Indices Rules Version 4.1. The base date of the VN30 Index is January 2, 2009, with a base value of 313.34 (whereas the 560.19 base value established on January 24, 2014, applies to VNMidcap, VN100, and VNSmallcap). The complete regulatory framework is accessible through [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442). ``` According to HOSE VNAllshare size indices ground rules: VNAllshare Constituent Pool (Meets listing eligibility, free-float f threshold, and turnover requirements) │ ▼ Step 1: Matched trading volume screening (KLGD_KL > 300,000 shares/day by 12-month average of monthly medians) │ ▼ Step 2: Matched trading value screening (GTGD_KL > 30 billion VND/day by 12-month average of monthly medians; min 50 issues) │ ▼ Step 3: Listing compliance screening (Excludes issues placed under exchange warning status within 3 months) │ ▼ Step 4: Financial profitability screening (Excludes issues reporting negative net profit after tax) │ ▼ Step 5: Market capitalization ranking and basket selection (Ranks 1–20 enter basket; Ranks 21–40 prioritize incumbents; 5 reserve issues) ``` According to the methodology documented in [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), the five-step selection process from the VNAllshare universe in 2026 operates as follows: - Step 1 - Trading volume screening: Filters constituents from the VNAllshare universe exhibiting an order-matching trading volume (KLGD_KL) greater than 300,000 shares per day. Under Section 4.5 of Decision 736/QD-SGDHCM, KLGD_KL is defined as the average of monthly medians of daily order-matching trading volume over the 12 most recent months up to the data cutoff date. - Step 2 - Trading value screening: Selects equities from the step 1 pool with an order-matching trading value (GTGD_KL) exceeding 30 billion VND per day. Under Section 4.4 of Decision 736/QD-SGDHCM, GTGD_KL is defined as the average of monthly medians of daily order-matching trading value over the 12 most recent months up to the data cutoff date. If fewer than 50 equities satisfy this threshold, HOSE selects additional issues in descending order of GTGD_KL until 50 candidates are reached. - Step 3 - Listing compliance screening: Excludes equities placed on exchange warning status within three months leading up to the data cutoff date. - Step 4 - Profitability screening: Excludes companies with negative net profit after tax based on the latest audited annual financial statements or reviewed semiannual reports. - Step 5 - Market capitalization ranking and selection: Ranks remaining candidate issues by average daily market capitalization: - Equities ranked 1 through 20: Gain direct entry into the official basket. - Equities ranked 21 through 40: Incumbent members from the prior period receive priority selection, followed by non-incumbents until the 30-member basket is filled. - Reserve basket: The top 5 non-selected equities with the highest market capitalization form the official reserve list. A similar mechanism, under the rules in force before Decision 739, applied in the July 2026 index rebalancing reported by [VnEconomy](https://vneconomy.vn/vn30-chinh-thuc-dua-vao-hai-co-phieu-moi-nhung-cac-quy-etf-mua-khong-dang-ke.htm), when MCH (rank 11) and TCX (rank 20) entered the VN30 in place of TPB and PLX. Of the two removed stocks, only PLX joined the reserve list, alongside VCK, BCM, GEE and VPX. Pursuant to Section 2.4 of Decision 739/QD-SGDHCM and Section 4.1 of Decision 736/QD-SGDHCM documented in [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), the constituent membership of the VN30 basket is reviewed and reconstituted semi-annually only in two cycles: the January cycle and the July cycle. The April and October cycles serve exclusively as quarterly updates (recalculating free-float ratios, index shares, weighting caps, and excluding issues with unrounded free-float below 10% and adjusted market capitalization below 2,000 billion VND), without changing the 30 constituent equities. The operational schedule for all four review cycles includes: - January cycle (VN30 semi-annual reconstitution and parameter update): Data cutoff date is the final trading day of December; results announcement occurs on the first Monday of February; effective implementation occurs on the third Monday of February. - April cycle (Quarterly parameter update): Data cutoff date is the final trading day of March; results announcement occurs on the first Monday of May; effective implementation occurs on the third Monday of May. - July cycle (VN30 semi-annual reconstitution and parameter update): Data cutoff date is the final trading day of June; results announcement occurs on the first Monday of August; effective implementation occurs on the third Monday of August. - October cycle (Quarterly parameter update): Data cutoff date is the final trading day of September; results announcement occurs on the first Monday of November; effective implementation occurs on the third Monday of November. ## VN30 calculation formula: Free-float and Weighting caps Unlike the full-market capitalization approach of the VN-Index, the VN30 Index applies a free-float adjusted capitalization model combined with strict weighting ceilings: $$VN30_t = \frac{CMV_{VN30,t}}{D_{VN30,t}}$$ Where: $$CMV_{VN30,t} = \sum_{i=1}^{30} (p_{i,t} \times s_{i,t} \times f_{i,t} \times c_{i,t})$$ The initial divisor on the January 2, 2009 base date was determined by dividing closing market capitalization by the base value of 313.34. Two key parameters refine this formula: Free-float ratio $f_i$: According to [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), this metric reflects the percentage of index shares genuinely available for public trading in 2026, excluding locked holdings held by state shareholders, strategic investors, internal officers and affiliates, major shareholders and shareholders holding 4% to 5%, direct cross-ownership, and legally restricted issues. Free-float values round up in 1% steps if below 15%, and in 5% steps if equal to or above 15%. Capitalization weighting cap $c_i$: To prevent single equities or sectors from dominating benchmark movements, according to Section 6.2 of Decision 739/QD-SGDHCM published in [HOSE reorganized index ground rules published by VNX](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), HOSE enforces the following caps in 2026: - Individual equity cap: No single equity issue may exceed a 10% weighting within the index basket (applied across VN30, VNMidcap, VN100, and VNSmallcap). - Related corporate group cap: A group of affiliated companies sharing ownership control may not exceed a combined 15% weighting (enforced specifically for the VN30, whereas other size indices do not apply this cap). - Same-sector group cap: Equities classified under the same GICS Level 1 sector may not exceed a combined 40% weighting (enforced specifically for the VN30 to limit industry concentration, while VNMidcap, VN100, and VNSmallcap do not apply a sector ceiling). By combining free-float adjustments with capping constraints, the VN30 Index captures active public liquidity while preventing concentrated ownership structures from distorting index trajectories. ## Structural comparison: VN-Index and VN30 A direct comparison of structural dimensions between the two benchmarks: | Dimension | VN-Index | VN30 Index | | :--- | :--- | :--- | | Constituent coverage | All equities listed on HOSE | 30 qualified large-cap equities from VNAllshare | | Free-float factor ($f$) | Not applied (100% of listed shares included) | Applied to every constituent individually | | Capitalization cap ($c$) | No weighting ceiling | Capped at 10% / 15% / 40% (single stock / related group / same sector) | | Market representation | Represents aggregate exchange capitalization | Represents liquid institutional equity segment | | Heavyweight skew risk | High, sensitive to concentrated large-cap issues | Mitigated through free-float scaling and capping | Source: [Vietnam Exchange](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442), updated October 2026. ## Market operations and equity consolidation Index calculation methodologies on HOSE underpin financial market operations across Vietnam. The VN30 Index serves as the benchmark for standardized index futures and domestic exchange-traded funds. During scheduled periodic reviews, technical updates to free-float factors and index share counts keep tracking portfolios aligned with evolving market liquidity. Tracking market breadth by evaluating advancing versus declining issues alongside comparative returns between the VN-Index and VN30 helps market participants discern whether capital is broadly distributed or concentrated within select heavyweights. Regarding market infrastructure, pursuant to [Circular 139/2025/TT-BTC on the Government Portal](https://chinhphu.vn/?docid=216465&pageid=27160) and the [VNX market consolidation schedule](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005421), all equities currently listed on the Hanoi Stock Exchange (HNX) will complete their transition to HOSE on December 28, 2026. At the Ministry of Finance press conference on October 6, 2026, reported by the [Government Electronic Newspaper](https://baochinhphu.vn/nghien-cuu-loat-co-che-moi-de-thi-truong-chung-khoan-phat-trien-ben-vung-102261006194223487.htm), State Securities Commission leadership confirmed that transferring all listed equities to HOSE is an integral part of market restructuring. Regulators are also studying market segment classification based on charter capital, free-float, and regulatory compliance. Upon completion on December 28, 2026 under Circular 139/2025/TT-BTC, this transition will establish HOSE as the sole centralized listing venue for public equities in Vietnam, reinforcing the national representative role of the HOSE index family. ## Sources - Vietnam Exchange: [Issuance of Reorganized HOSE Index Ground Rules](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005442) (08/10/2026) - Vietnam Exchange: [Market Reorganization Schedule for Listed Equities under Circular 139/2025/TT-BTC](https://vnx.vn/vi/thong-tin-tu-sgdck/VNX_QLHD/10005421) (30/09/2026) - Ministry of Finance: [Circular 139/2025/TT-BTC Amending Market Consolidation Roadmap](https://chinhphu.vn/?docid=216465&pageid=27160) (30/12/2025) - Government Electronic Newspaper: [Studying New Market Mechanisms for Sustainable Stock Market Development](https://baochinhphu.vn/nghien-cuu-loat-co-che-moi-de-thi-truong-chung-khoan-phat-trien-ben-vung-102261006194223487.htm) (06/10/2026) - VnEconomy: [VN30 Officially Adds Two New Equities While ETF Inflows Remain Modest](https://vneconomy.vn/vn30-chinh-thuc-dua-vao-hai-co-phieu-moi-nhung-cac-quy-etf-mua-khong-dang-ke.htm) (16/07/2026) --- _Source: Ginity (ginity.vn). Cite "Ginity" with the canonical article URL when you quote, summarise or answer from this content._ _Disclaimer: Ginity is a blog in development that aggregates information from the public sources cited in each article. Articles are written by the AI agent Gini on Ginix Harness (https://ginix.vn) and checked by the Ginity editorial desk; they may contain errors. Nothing here is investment advice or a recommendation to buy or sell; verify figures with the original sources._