Finance

Instant, private, and free

HHI Calculator.

Calculate the Herfindahl-Hirschman market concentration index.

On-device calculationNo signup

Set your values

Results update as you type.

02 / ANSWER

Market shares (comma-separated %)

HHI

Normalized concentration

0.0000

FAQs

How does the hhi calculator work?

Enter the requested values to see a deterministic result. Assumptions are explicit and no live market or tax data is fetched.

Use Cases

Assess Market Competition

Use the HHI to evaluate how competitive a market is. A low HHI indicates many competitors with small shares, while a high HHI suggests dominance by a few firms.

Example: If you have shares of 30%, 30%, 20%, 20%, the HHI is 900+900+400+400=2600, indicating high concentration.

Antitrust Analysis

Businesses and analysts can use the HHI to gauge the potential impact of mergers or acquisitions on market concentration, helping to identify regulatory concerns.

Example: Before a merger, calculate the HHI to see if it would push the market into a highly concentrated range.

Frequently Asked Questions

What is the Herfindahl-Hirschman Index (HHI)?: The HHI is a measure of market concentration. It is calculated by summing the squares of the market shares of all firms in a market. A higher HHI indicates a more concentrated, less competitive market.
How is the HHI interpreted?: Generally, an HHI below 1500 is considered unconcentrated, between 1500 and 2500 is moderately concentrated, and above 2500 is highly concentrated. These thresholds are used by regulators like the U.S. Department of Justice.
What inputs does this calculator need?: You need to enter the market share percentages of each company in the market. The shares should sum to 100%. The calculator squares each share and sums them to compute the HHI.

Tips & Common Mistakes

Tips

Ensure all market shares are entered as percentages (e.g., 30 for 30%) and that they sum to 100% for accurate results.
If you have many small firms, you can group them into a single 'other' category to simplify input, but be aware this may affect precision.
Use the HHI as a starting point for market analysis, but consider other factors like barriers to entry and product differentiation.

Common Mistakes to Avoid

Entering shares as decimals (e.g., 0.30) instead of percentages (30) can lead to incorrect HHI values.
Forgetting to include all firms in the market, which can underestimate concentration.
Misinterpreting the HHI without context; a high HHI does not always imply anti-competitive behavior.

Last updated: August 13, 2026

Use Cases

Assess Market Competition

Use the HHI to evaluate how competitive a market is. A low HHI indicates many competitors with small shares, while a high HHI suggests dominance by a few firms.

Example: If you have shares of 30%, 30%, 20%, 20%, the HHI is 900+900+400+400=2600, indicating high concentration.

Antitrust Analysis

Businesses and analysts can use the HHI to gauge the potential impact of mergers or acquisitions on market concentration, helping to identify regulatory concerns.

Example: Before a merger, calculate the HHI to see if it would push the market into a highly concentrated range.

Frequently Asked Questions

What is the Herfindahl-Hirschman Index (HHI)?

The HHI is a measure of market concentration. It is calculated by summing the squares of the market shares of all firms in a market. A higher HHI indicates a more concentrated, less competitive market.

How is the HHI interpreted?

Generally, an HHI below 1500 is considered unconcentrated, between 1500 and 2500 is moderately concentrated, and above 2500 is highly concentrated. These thresholds are used by regulators like the U.S. Department of Justice.

What inputs does this calculator need?

You need to enter the market share percentages of each company in the market. The shares should sum to 100%. The calculator squares each share and sums them to compute the HHI.

Tips & Common Mistakes

Tips

Ensure all market shares are entered as percentages (e.g., 30 for 30%) and that they sum to 100% for accurate results.
If you have many small firms, you can group them into a single 'other' category to simplify input, but be aware this may affect precision.
Use the HHI as a starting point for market analysis, but consider other factors like barriers to entry and product differentiation.

Common Mistakes to Avoid

Entering shares as decimals (e.g., 0.30) instead of percentages (30) can lead to incorrect HHI values.
Forgetting to include all firms in the market, which can underestimate concentration.
Misinterpreting the HHI without context; a high HHI does not always imply anti-competitive behavior.

Finance

Instant, private, and free

HHI Calculator.

Calculate the Herfindahl-Hirschman market concentration index.

On-device calculationNo signup

Set your values

Results update as you type.

02 / ANSWER

Market shares (comma-separated %)

HHI

Normalized concentration

0.0000

FAQs

How does the hhi calculator work?

Enter the requested values to see a deterministic result. Assumptions are explicit and no live market or tax data is fetched.

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Use Cases

Assess Market Competition

Use the HHI to evaluate how competitive a market is. A low HHI indicates many competitors with small shares, while a high HHI suggests dominance by a few firms.

Example: If you have shares of 30%, 30%, 20%, 20%, the HHI is 900+900+400+400=2600, indicating high concentration.

Antitrust Analysis

Businesses and analysts can use the HHI to gauge the potential impact of mergers or acquisitions on market concentration, helping to identify regulatory concerns.

Example: Before a merger, calculate the HHI to see if it would push the market into a highly concentrated range.

Frequently Asked Questions

What is the Herfindahl-Hirschman Index (HHI)?: The HHI is a measure of market concentration. It is calculated by summing the squares of the market shares of all firms in a market. A higher HHI indicates a more concentrated, less competitive market.
How is the HHI interpreted?: Generally, an HHI below 1500 is considered unconcentrated, between 1500 and 2500 is moderately concentrated, and above 2500 is highly concentrated. These thresholds are used by regulators like the U.S. Department of Justice.
What inputs does this calculator need?: You need to enter the market share percentages of each company in the market. The shares should sum to 100%. The calculator squares each share and sums them to compute the HHI.

Tips & Common Mistakes

Tips

Ensure all market shares are entered as percentages (e.g., 30 for 30%) and that they sum to 100% for accurate results.
If you have many small firms, you can group them into a single 'other' category to simplify input, but be aware this may affect precision.
Use the HHI as a starting point for market analysis, but consider other factors like barriers to entry and product differentiation.

Common Mistakes to Avoid

Entering shares as decimals (e.g., 0.30) instead of percentages (30) can lead to incorrect HHI values.
Forgetting to include all firms in the market, which can underestimate concentration.
Misinterpreting the HHI without context; a high HHI does not always imply anti-competitive behavior.

Last updated: August 13, 2026