Finance

HHI Calculator (Herfindahl-Hirschman Index)

Measure market concentration by summing the squared market shares of all firms.

Enter market share (%) for each firm:

Firm 1 (%)

Firm 2 (%)

Firm 3 (%)

Firm 4 (%)

Firm 5 (%)

Remaining Others (%)

Formula:
HHI = Σ(market share %)²
Range: 0 (perfect competition) to 10,000 (monopoly)
DOJ Thresholds: <1,500 = Competitive, 1,500-2,500 = Moderate, >2,500 = Concentrated

HHI in Antitrust

The Department of Justice uses HHI to evaluate mergers. A merger that increases HHI by more than 200 points in a concentrated market (>2,500) is likely to face scrutiny.