What free float means

A listed company’s shares aren’t all equally “on the market”. A big block usually sits with the promoters — the founders or parent group who control the company and are named as such in its filings. Other blocks may be held by the government in a strategic role, a foreign parent, or an employee trust. None of those holders is likely to sell on an ordinary day.

Free float is what’s left: the shares realistically available to ordinary investors. Free-float market cap is the market cap of just that part.

Every listed company files its shareholding pattern with the exchanges each quarter, splitting holders into “promoter and promoter group” and “public”. That filing is where both numbers start (the promoter holding post covers what else to read in it, pledges included).

Why it matters: index providers weight stocks by free-float market cap. NSE Indices determines each company’s investible weight factor (IWF) from the shareholding in that quarterly pattern, excluding a long list of holdings unlikely to trade — promoter-group holdings, strategic stakes by corporate bodies, government holdings, foreign direct investment, employee-benefit trusts, locked-in shares and more (NSE Indices, Methodology Document for Equity Indices, September 2026). The Nifty 50 has been weighted this way since 26 June 2009 (same document).

The formula

Free float (%)          = Shares not held by promoters or other locked-up holders
                          ÷ Total shares × 100
Free-float market cap   = Full market cap × Free float (%)
                        = Full market cap × IWF          (index providers' version)

Index weight of a stock = Its free-float market cap ÷ Sum of all constituents' free-float market caps

The simple version here uses “not promoter” as free float. NSE’s IWF excludes more, so an index’s free float for a company is usually a little lower than 100% minus promoter holding.

Worked example: Britannia

At 31 March 2025, Britannia’s promoter and promoter group — the Wadia group entities — held 12,17,52,892 of its 24,08,68,296 shares (Annual Report 2024-25, standalone financial statements, note on shareholding of promoters). Price is the 30 June 2025 NSE close; for illustration only.

 
Promoter and promoter group 50.55%
Everyone else (simple free float) 49.45%
Full market cap at ₹5,851 ₹1,40,951 crore
Free-float market cap (simple) ₹69,704 crore

Roughly half of Britannia’s market value never really trades. In an index weighted by full market cap it would count at twice the weight its tradable shares justify.

Worked example: Desi Bites

Desi Bites’ fictional shareholding pattern, as of 31 December 2025, at the ₹640 listing price:

Shares (lakh) %
Promoters 10 80%
Public 2.5 20%
Total 12.5 100%
Full market cap ₹80 crore  
Free-float market cap ₹16 crore  

Only a fifth of Desi Bites is in public hands. That’s thin: a small float is one reason a small company’s price can swing on little volume.

It is also, in the real world, too thin. Indian rules require every listed company to keep public shareholding of at least 25%, and to restore it within 12 months if it falls below (Securities Contracts (Regulation) Rules, 1957, Rule 19A, as amended to 13 March 2026). A company of Desi Bites’ size would also have had to offer at least 25% in its IPO (Rule 19(2)(b)). Our case study simplifies this: a real Desi Bites would need to find another 62,500 shares for the public, typically by promoters selling some — one of the routes the OFS post describes. Very large companies get longer to reach 25%; the 13 March 2026 amendment set new, staggered timelines by size.

Why weights use free float

Two made-up companies, identical full market caps:

Full market cap Free float Free-float market cap Weight (full) Weight (free float)
Company P (widely held) 1,000 90% 900 50% 75%
Company Q (promoter-heavy) 1,000 30% 300 50% 25%

An index fund tracking a full-cap index would have to buy equal amounts of both — but Q only has 30% of its shares available, so the fund’s buying would push Q’s price around far more. Weighting by free float makes an index something funds can actually replicate, and it’s why the Nifty 50 also requires constituents to be liquid: an average impact cost of 0.50% or less on a ₹10 crore basket for 90% of observations (NSE Indices methodology; impact cost is explained in the bid-ask spread post).

Common mistakes

  • Treating a high promoter holding as automatically good or bad. High promoter holding can mean skin in the game; it also means a small float and less say for minority shareholders. The trend (and any pledges) says more than the level.
  • Using full market cap to judge how big a stock is in an index. A company with a large full market cap and a small float can carry a modest index weight. Index weights, and so index-fund buying, follow free float.
  • Mixing the two in size labels. SEBI’s large/mid/small-cap buckets rank companies by full market cap; index weights use free-float market cap. A stock can be “large cap” and still a small index weight.
  • Assuming “public” means “retail”. The public category includes mutual funds, insurers and foreign portfolio investors, who may hold large, rarely traded blocks. Free float is an estimate of what could trade, not what does.

Takeaway: free float is the part of a company’s shares outside promoters’ and other locked-up hands — the part that actually trades. Index weights are built on it, which is why a company with half its shares held by promoters counts for about half its market cap in the Nifty.