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Herfindahl-Hirschman Index Calculator

Calculate HHI by summing the squared market shares of up to five firms.

Runs locally

Inputs and results stay in this browser. Currency symbols are illustrative; use any consistent currency.

HHI2,458

Listed shares cover the full market

Listed market share100%
Unlisted share0%

Understand HHI market concentration

One idea, three depths

Choose how deeply to explain HHI market concentration

HHI market concentration: Calculate HHI by summing the squared market shares of up to five firms.

Age 5Explain it to a 5-year-oldStart with a picture

Imagine using HHI market concentration to answer this question: calculate hhi by summing the squared market shares of up to five firms? Enter Firm 1 market share, Firm 2 market share, Firm 3 market share, and 2 other inputs; the calculator shows HHI. For example: Shares of 35%, 25%, 20%, 12% and 8% sum to 100% and produce an HHI of 2,458. The answer tells you HHI.

Age 15Explain it to a 15-year-oldConnect it to the formula

HHI ranges from near zero for highly fragmented markets to 10,000 for a monopoly. Enter the firms being analysed; omitted smaller firms make the result a lower-bound estimate. The rule is HHI = share₁² + share₂² + … + shareₙ², with percentage shares entered from 0 to 100. Its input values are Firm 1 market share (%), Firm 2 market share (%), Firm 3 market share (%), Firm 4 market share (%), Firm 5 market share (%), and the main result is HHI. For example: Shares of 35%, 25%, 20%, 12% and 8% sum to 100% and produce an HHI of 2,458.

CollegeExplain it at college levelState the model precisely

This calculator evaluates a microeconomics relationship while holding unmodelled conditions constant. The implemented relation is HHI = share₁² + share₂² + … + shareₙ², with percentage shares entered from 0 to 100, evaluated from Firm 1 market share (%), Firm 2 market share (%), Firm 3 market share (%), Firm 4 market share (%), Firm 5 market share (%) to produce HHI. HHI ranges from near zero for highly fragmented markets to 10,000 for a monopoly. Enter the firms being analysed; omitted smaller firms make the result a lower-bound estimate. The result depends on comparable definitions, units, populations and time periods. It estimates a relationship; it does not establish causation or replace current primary data.

The economic question

Calculate HHI by summing the squared market shares of up to five firms.

Why this relationship is useful

HHI ranges from near zero for highly fragmented markets to 10,000 for a monopoly. Enter the firms being analysed; omitted smaller firms make the result a lower-bound estimate.

Inputs that must be comparable

  • Firm 1 market share (minimum 0) measured in %.
  • Firm 2 market share (minimum 0) measured in %.
  • Firm 3 market share (minimum 0) measured in %.
  • Firm 4 market share (minimum 0) measured in %.
  • Firm 5 market share (minimum 0) measured in %.

Use one market, firm, population and time period throughout; mixing definitions can make a correctly calculated number economically meaningless.

The model

HHI = share₁² + share₂² + … + shareₙ², with percentage shares entered from 0 to 100

From inputs to output

The calculator combines Firm 1 market share, Firm 2 market share, Firm 3 market share, Firm 4 market share, Firm 5 market share and reportsHHI together with Listed market share, Unlisted share. Change one assumption at a time to identify what actually drives the estimate.

How to read HHI

Read the sign, magnitude, unit and period together. The result quantifies the relationship in “calculate hhi by summing the squared market shares of up to five firms”; it does not by itself prove that one input caused another.

A worked economic example

Shares of 35%, 25%, 20%, 12% and 8% sum to 100% and produce an HHI of 2,458.

Where interpretation can fail

Do not use the result when the input definitions, units or formula assumptions do not match the real situation. This is an educational model, not financial, investment, tax or policy advice; verify material decisions against primary data and professional guidance.

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Supporting sourcesAcademic referencesPrimary standards, textbooks and complete citations

Standards, reading and academic references

Use the calculator as the worked interaction, then consult the primary standards and academic textbooks listed below. MW SysArc links to the original sources; the explanation on this page is original and does not reproduce them.

Principles of Economics 3e

Read the free OpenStax economics textbook
Cite this book
APA 7
Greenlaw, S. A., Shapiro, D., & MacDonald, D. (2022). Principles of economics 3e. OpenStax. https://openstax.org/books/principles-economics-3e/pages/1-introduction
MLA 9
Greenlaw, Steven A., et al. Principles of Economics 3e. OpenStax, 2022, https://openstax.org/books/principles-economics-3e/pages/1-introduction.
Chicago author-date
Greenlaw, Steven A., David Shapiro, and Daniel MacDonald. 2022. Principles of Economics 3e. Houston, TX: OpenStax. https://openstax.org/books/principles-economics-3e/pages/1-introduction.

OpenStax entries are free to read online. Follow the licence shown on each linked source before redistributing or adapting its content.

Reuse the page responsiblyCite this pageAPA, MLA, Chicago, Harvard, BibTeX and RIS

These formats cite this calculator page itself. They are separate from the academic references above, which support the mathematical method and terminology.

Organizational author: MW SysArc. Published:. Canonical page:https://economics.mwsysarc.com/micro/herfindahl-hirschman-index.

APA 7

MW SysArc. (2026, July 21). Herfindahl-Hirschman Index Calculator. MW SysArc Tools. https://economics.mwsysarc.com/micro/herfindahl-hirschman-index

MLA 9

MW SysArc. “Herfindahl-Hirschman Index Calculator.” MW SysArc Tools, 21 July 2026, https://economics.mwsysarc.com/micro/herfindahl-hirschman-index. Accessed 31 Aug. 2026.

Chicago 17

MW SysArc. “Herfindahl-Hirschman Index Calculator.” MW SysArc Tools. Published July 21, 2026. Accessed August 31, 2026. https://economics.mwsysarc.com/micro/herfindahl-hirschman-index.

Harvard

MW SysArc (2026) ‘Herfindahl-Hirschman Index Calculator’, MW SysArc Tools. Published 21 July 2026. Available at: https://economics.mwsysarc.com/micro/herfindahl-hirschman-index (Accessed: 31 August 2026).

BibTeX and RIS records

BibTeX

@misc{mwsysarc_hhi_2026,
  author = {{MW SysArc}},
  title = {Herfindahl-Hirschman Index Calculator},
  howpublished = {MW SysArc Tools},
  year = {2026},
  url = {https://economics.mwsysarc.com/micro/herfindahl-hirschman-index},
  note = {Published July 21, 2026; accessed August 31, 2026}
}

RIS

TY  - ELEC
AU  - MW SysArc
TI  - Herfindahl-Hirschman Index Calculator
T2  - MW SysArc Tools
PY  - 2026
DA  - 2026-07-21
Y2  - 2026-08-31
UR  - https://economics.mwsysarc.com/micro/herfindahl-hirschman-index
N1  - Published July 21, 2026
ER  -

Clear answers

Frequently asked questions

What does the HHI market concentration do?

Calculate HHI by summing the squared market shares of up to five firms.

How does the HHI market concentration work?

The calculator applies this formula: HHI = share₁² + share₂² + … + shareₙ², with percentage shares entered from 0 to 100. HHI ranges from near zero for highly fragmented markets to 10,000 for a monopoly. Enter the firms being analysed; omitted smaller firms make the result a lower-bound estimate.

What can I learn from the HHI market concentration?

It helps you explore the relationship described by this tool: Calculate HHI by summing the squared market shares of up to five firms. Change one input at a time to observe how it affects the result.

Does MW SysArc receive or store what I enter?

No. The calculation runs locally in your browser. MW SysArc does not receive or store your calculation inputs.

How should I use the result?

Use the result as an estimate or educational aid. Check important financial, business or policy decisions with qualified sources and current data.

Last reviewed . Calculations tested .

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