Market share and HHI calculator
Enter the size of each business using any consistent measure (revenue, customers, review counts, website visits or outlets). The calculator returns each share, the HHI, the four-firm concentration ratio and what the level usually means for strategy.
How to use it
- Pick the measure you are using (it only labels the results).
- Enter one row per business. Values like 1.2M, 3 lakh or 2 crore are understood.
- Tick “You” on your row to see your rank.
- Read HHI, CR4 and the concentration level.
Method
Each share is the business's value divided by the total of all rows. HHI is the sum of the squared percentage shares (0 to 10,000). Levels follow the 2023 US Merger Guidelines: above 1,800 is highly concentrated, 1,000 to 1,800 moderately concentrated, below 1,000 unconcentrated. CR4 is the combined share of the four largest businesses.
Worked example
Shares of 40%, 30%, 20% and 10% give an HHI of 1,600 + 900 + 400 + 100 = 3,000: highly concentrated. Ten businesses with 10% each give 1,000: the edge of moderately concentrated.
How to read the result
In fragmented markets a focused specialist can take share quickly. In concentrated markets the leaders set prices and expectations, so smaller players do better by owning a segment the leaders serve poorly.
Limitations
- Shares describe the businesses you enter, not the whole market, unless you include everyone.
- Proxies such as reviews or traffic are estimates; use the same proxy for every row.
- The thresholds are strategy rules of thumb here, not legal or antitrust advice.