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HHI Calculator

Calculate the Herfindahl-Hirschman Index (HHI) to measure market concentration and competition.
What This Calculator Helps You Do
Use the inputs below to test scenarios, compare outcomes, and interpret the result before acting on it.

HHI Calculator is designed to give you a fast answer, but it also provides supporting context such as formulas, worked examples, FAQs, and charts so the result is easier to validate.

For the best result, use realistic input values, review the assumptions in the explanation panels, and compare multiple scenarios if you are planning a decision based on the output.

Decision Context
Page-specific guidance for using this result in a real planning decision.

This finance calculator is intended to turn a specific business or money question into a repeatable estimate that is easier to compare and review.

Use it when you need a fast planning baseline before moving into a spreadsheet, lender discussion, management review, or more formal analysis.

The result is most useful when tested against several realistic assumptions, because financial decisions are usually sensitive to more than one input at a time.

Calculator
Enter your values
Company A
Company B
Company C
Company D
Company E
Analysis
Interpretation of the current calculator output

Enter values to see detailed analysis and insights.

How to Use

Step-by-step instructions
  1. 1Enter the market share percentage for each major company
  2. 2Add or remove companies as needed
  3. 3Ensure total market share sums to 100% for accuracy
  4. 4Review the HHI score and concentration level

HHI Formula

Sum of the squares of the market shares of the firms within the industry. Ranges from near 0 to 10,000.
HHI = Σ (Market Share %²)

Variables:

sMarket share of each firm (as a whole number, e.g., 30 for 30%)
nNumber of firms in the market

Example

Market Analysis

Inputs:

Firm A:30%
Firm B:30%
Firm C:20%
Firm D:20%

Steps:

  1. 1.HHI = 30² + 30² + 20² + 20²
  2. 2.HHI = 900 + 900 + 400 + 400
  3. 3.HHI = 2,600
Result:
2,600 (Highly Concentrated)

Frequently Asked Questions

What is HHI used for?

Regulators (like the DOJ) use it to evaluate mergers. If a merger increases HHI significantly in a concentrated market, it may be blocked.

What are the thresholds?

Below 1,500: Unconcentrated. 1,500 to 2,500: Moderately Concentrated. Above 2,500: Highly Concentrated.

Why square the shares?

Squaring gives more weight to firms with larger market shares, reflecting their greater impact on competition.
In-depth guideBrowse Financial calculators
HHI Calculator Guide
Detailed usage notes, assumptions, mistakes to avoid, and related tools.

HHI Calculator helps turn the available inputs into a result that is easier to check, compare, and explain. Calculate the Herfindahl-Hirschman Index (HHI) to measure market concentration and competition.

Use this page as part of the broader financial workflow when you need a repeatable calculation instead of a one-off estimate.

Formula And Variables
How the calculator turns inputs into an answer.

HHI Formula is the main method behind this calculator. The equation is HHI = Σ (Market Share %²), and the calculator applies it consistently as you change the inputs.

The most important variables are: s is market share of each firm (as a whole number, e.g., 30 for 30%), n is number of firms in the market. Check those values first if the output looks higher or lower than expected.

How To Use The Result
What to compare before acting on the output.

The worked example on this page uses Firm A = 30%, Firm B = 30%, Firm C = 20%, Firm D = 20% and produces 2,600 (Highly Concentrated). Use that example as a quick check for the calculation flow before entering your own values.

For practical use, read the hhi calculator result as a decision-support number. It is strongest when you compare two or more scenarios using the same units and assumptions.

Data Visualization And Analysis
Different chart views answer different questions about the same calculator output.

Best ways to read the charts

Use a bar chart when you need to compare separate result components, a line or area chart when the output changes across steps or time, and a pie-style distribution when every value is part of one total.

When the page shows multiple chart tabs, start with the overview, then check the ranking view to see which value drives the result most strongly.

What the analysis should tell you

Compare the average, range, highest value, lowest value, and dominant contributor before making a conclusion from the main number alone.

If one value contributes most of the total, test that assumption first. If values are spread evenly, the result is usually driven by the full input set rather than a single outlier.

Common Mistakes
  • Do not mix units unless the calculator explicitly converts them for you.
  • Avoid copying a result without checking whether the inputs describe the same time period, measurement system, or scenario.
  • If the answer looks surprising, change one input at a time so you can identify which assumption is driving the output.
When The Result May Be Inaccurate

The result can be inaccurate if inputs use mixed units, rounded source data, outdated rates, or assumptions that do not match the situation being modeled.

Run a second scenario with conservative inputs when the output will affect a purchase, project, health decision, academic answer, or financial plan.

HHI Calculator is an educational planning tool. It should not replace advice from a qualified professional who can review the full context and current rules.

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Additional Questions

How accurate is HHI Calculator?

HHI Calculator is accurate for the formula and inputs shown on the page. Real-world accuracy depends on whether the values you enter are complete, current, and measured in the expected units.

What should I check before using the hhi calculator result?

Check the input units, review the formula section, compare the worked example, and run at least one alternate scenario if the result will support a decision.