Index Weighting and Float Methodology

Index weighting, float-adjusted capitalization, price weighting, and benchmark market-cap statistics.

Index Weighting and Float Methodology explains how benchmark providers convert eligible securities into constituent weights. Free-float capitalization and free-float methodology are covered together in the float-adjusted market-capitalization guide.

Use this branch when benchmark selection, index membership, weighting, float adjustment, publication source, region, sector, or dividend treatment changes the comparison being made.

Key Terms in This Branch

TermUse it for
Capitalization-weighted IndexHow company market values determine constituent weights.
Float-Adjusted Market CapitalizationFree-float value, investable weight factors, ownership exclusions, and index-weight calculations.
Price-Weighted IndexAn alternative method in which nominal share prices determine index influence.
Weighted Average Market CapitalizationA portfolio or fund statistic summarizing the market-cap profile of holdings.

What to Check

Check the index provider, universe, eligibility rule, weighting method, float adjustment, rebalancing schedule, currency, dividend treatment, data date, and whether the index is investable or only a benchmark.

Common Mistakes

  • Treating an index as a recommendation or as a directly owned portfolio.
  • Comparing index returns without checking currency, dividends, fees, and time period.
  • Ignoring methodology changes, reconstitution, concentration, and float adjustments.
  • Using a regional or sector index as a broad-market benchmark without checking its universe.

Indexes are benchmarks and data tools, not personalized investment recommendations or performance promises.

In this section

Choose a subsection first. Deeper term pages live inside each subsection, which keeps large topic hubs readable.

Capitalization-Weighted Index

A capitalization-weighted index assigns larger weights to companies with larger full or float-adjusted market values. See formulas, examples, and risks.

Float-Adjusted Market Capitalization

Float-adjusted market capitalization values shares available to public investors. Learn the formula, free-float methodology, index weights, and limits.

Price-Weighted Index

A price-weighted index gives each constituent influence in proportion to its quoted share price, not its company size or public float.

Weighted Average Market Cap

Weighted average market capitalization summarizes the company-size exposure of a portfolio. Compare arithmetic, geometric, and median methods.

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