Available Slot
NetGrow

HHI Calculator (Herfindahl-Hirschman Index)

Calculate HHI from market shares. Measure market concentration (unconcentrated to highly concentrated).

Use the HHI Calculator (Herfindahl-Hirschman Index)

Enter market shares by firm. HHI, top firm share, and concentration band are calculated.

Market shares

Firm name (optional) and market share. Input as % (e.g. 30) or decimal (e.g. 0.30).

Results

HHI
3000
Concentration
Highly concentrated
Top firm share (%)
40.0
Top 3 combined (%)
90.0

HHI = Σ(share_i²) with shares in percentage points. Common guidance: <1500 unconcentrated, 1500–2500 moderate, ≥2500 high. Not legal advice.

What this metric means

HHI summarises market concentration by squaring each firm's share and summing. It gives more weight to large players and is used in competition and merger review.

How to calculate it

HHI = Σ(share_i²). Use shares in percentage points (e.g. 40 not 0.40). If you have decimals, multiply by 100 first or use the decimal input option.

How to improve the metric

HHI describes the market; firms don't typically 'improve' it directly. Lower HHI means more competitors or more even shares. Strategy depends on your position and goals.

Common mistakes

Using revenue instead of share; mixing % and decimal; or including too few players so shares don't represent the full market.

How to interpret your result

Compare to regulatory thresholds and to prior periods. Rising HHI may indicate consolidation. Use with top-firm and top-3 share for context.

FAQs

What is the HHI?▾
HHI = sum of squared market shares (in percentage points). It measures market concentration. Higher values mean fewer, larger players.
How do I enter shares?▾
Enter each firm's share as a percentage (e.g. 30) or as a decimal (e.g. 0.30). Toggle 'Share as %' vs 'Share as decimal' and optionally normalise to 100%.
What do the concentration bands mean?▾
Common guidance: HHI < 1500 unconcentrated, 1500–2500 moderately concentrated, ≥ 2500 highly concentrated. This is not legal advice; regulators use HHI as one input.
Why normalise to 100%?▾
If your shares don't sum to 100%, normalising rescales them so they do. Use when you have a subset of the market or rounding errors.

Related tools

Browse all calculators on NetGrow.

NetGrow

HHI Calculator (Herfindahl-Hirschman Index)

Calculate HHI from market shares. Measure market concentration (unconcentrated to highly concentrated).

Use the HHI Calculator (Herfindahl-Hirschman Index)

Enter market shares by firm. HHI, top firm share, and concentration band are calculated.

Market shares

Firm name (optional) and market share. Input as % (e.g. 30) or decimal (e.g. 0.30).

Results

HHI
3000
Concentration
Highly concentrated
Top firm share (%)
40.0
Top 3 combined (%)
90.0

HHI = Σ(share_i²) with shares in percentage points. Common guidance: <1500 unconcentrated, 1500–2500 moderate, ≥2500 high. Not legal advice.

What this metric means

HHI summarises market concentration by squaring each firm's share and summing. It gives more weight to large players and is used in competition and merger review.

How to calculate it

HHI = Σ(share_i²). Use shares in percentage points (e.g. 40 not 0.40). If you have decimals, multiply by 100 first or use the decimal input option.

How to improve the metric

HHI describes the market; firms don't typically 'improve' it directly. Lower HHI means more competitors or more even shares. Strategy depends on your position and goals.

Common mistakes

Using revenue instead of share; mixing % and decimal; or including too few players so shares don't represent the full market.

How to interpret your result

Compare to regulatory thresholds and to prior periods. Rising HHI may indicate consolidation. Use with top-firm and top-3 share for context.

FAQs

What is the HHI?▾
HHI = sum of squared market shares (in percentage points). It measures market concentration. Higher values mean fewer, larger players.
How do I enter shares?▾
Enter each firm's share as a percentage (e.g. 30) or as a decimal (e.g. 0.30). Toggle 'Share as %' vs 'Share as decimal' and optionally normalise to 100%.
What do the concentration bands mean?▾
Common guidance: HHI < 1500 unconcentrated, 1500–2500 moderately concentrated, ≥ 2500 highly concentrated. This is not legal advice; regulators use HHI as one input.
Why normalise to 100%?▾
If your shares don't sum to 100%, normalising rescales them so they do. Use when you have a subset of the market or rounding errors.

Related tools

Browse all calculators on NetGrow.