Four-firm concentration ratio
How much of a market belongs to its four biggest companies?
Add the market shares of the four largest companies. The result, called CR4, tells you how much of that market they account for together.
Try the exampleFive coffee companies.
One fictional market.
The biggest four account for 90% of sales. The fifth accounts for the remaining 10%.
Try it with your market.
Replace the example with each company’s share of the same market. Enter the whole market, totaling 100%; we’ll find the four largest.
Add four shares. Keep the whole market in view.
Put the companies in order from largest to smallest, then add the first four market shares. If you start with sales instead of percentages, divide those four companies’ combined sales by total market sales and multiply by 100.
Use the same product, geographic area, period and measure for every company. Revenue shares and unit-sales shares answer different questions. Count firms, not individual stores belonging to the same firm.
This calculator asks for the complete market so it can identify the largest four. If you already know the true top four and their shares of the whole market, you can add them directly. Do not treat an unknown “other” group as one company.
Sources: US Census Bureau.
A high CR4 is a starting point, not a verdict.
A CR4 of 90% means four companies account for 90% of the market you defined. It does not tell you how intensely they compete, how easy it is to enter, or whether customers can switch to substitutes.
The number does not prove unlawful conduct, establish a durable economic moat or predict investment returns. There is no legal label assigned by this calculator.
With fewer than four firms in a complete market, this calculator adds all of them. Small rounding differences of up to 0.05 percentage points in the total are accepted; the entered percentages are never rescaled.
Sources: US Census Bureau; US Department of Justice.
How is CR4 different from HHI?
CR4 adds the four largest shares. HHI squares every individual company’s share and then adds those squares. It gives more weight to a very large firm.
| Company shares | CR4 | HHI |
|---|---|---|
| 25, 25, 25, 15, 10% | 90% | 2,200 |
| 60, 10, 10, 10, 10% | 90% | 4,000 |
CR4 treats the two markets alike. HHI distinguishes the second market’s much larger leader. Neither number replaces the evidence about actual competition.
Explore the HHI calculator or read the DOJ’s calculation method.
Sources and method
The examples on this page are fictional and calculated from the shares shown. They are not estimates of a real industry.
- How the Census Bureau uses four-firm concentration ratiosUS Census Bureau
- The HHI calculationUS Department of Justice
- Why the market definition mattersUS Department of Justice
Sources checked September 13, 2026. Educational examples, not investment advice.