Four-firm concentration ratio:

Four-Firm Concentration Ratio Calculator

Market Share of Firm 1 (%): Market Share of Firm 2 (%): Market Share of Firm 3 (%): Market Share of Firm 4 (%):

HHI Calculator:

Herfindahl-Hirschman Index (HHI) Calculator

Enter the market share (%) for each firm (up to 8 firms):

Firm 1: %
Firm 2: %
Firm 3: %
Firm 4: %
Firm 5: %
Firm 6: %
Firm 7: %
Firm 8: %

The Herfindahl–Hirschman index

An exam question on the market spectrum sometimes includes a graphical representation of the market share data. You can use this graph to work out the degree of market concentration in the industry. The video below shows you how. 

The Herfindahl–Hirschman index

The Herfindahl-Hirschman Index establishes the degree of market concentration in a given industry. The video shows you how to calculate the necesary coefficient.