A market cap calculator multiplies a share price by a share count. That is the whole of it, and the arithmetic is not why anyone gets it wrong. The errors come from the share count — which count, as at when, including what — and from the widespread habit of treating the result as the value of the company rather than the value of its equity at the price of the last few shares that changed hands.
Arb Digital publishes this in the free tools library beside the enterprise value calculator, and the boundary between them is the single most useful thing to understand here. Market cap prices the equity. Enterprise value adds net debt to give what the whole business costs on a capital-structure-neutral basis. A company with heavy borrowings can have a modest market cap and a very large enterprise value, and comparing two companies on market cap alone quietly assumes their balance sheets look the same.
What This Market Cap Calculator Does
It gives three figures rather than one, because three are used in practice and they are not interchangeable.
The basic market cap is price multiplied by shares outstanding. This is the headline number quoted everywhere. The free-float market cap subtracts shares held by affiliates, founders, controlling families and strategic holders, leaving only shares actually available to trade — this is the basis major index providers use for weighting, and it is what determines how much of a company an index fund needs to buy. The fully diluted market cap adds shares that would come into existence if outstanding options, restricted stock units and convertible instruments were exercised, which is the relevant figure when comparing valuation against per-share metrics that use a diluted count.
It also reports the free float as a percentage and applies a conventional size band. The page makes no judgement about whether any capitalisation is high, low, expensive or cheap, and no statement about where any share price will go.
How to Use It
- Take the share count from the filing cover page, not from a headline. Companies state shares outstanding as at a specific recent date on the front of the annual or quarterly report. That figure is net of treasury stock, which is what you want.
- Check for multiple share classes. A dual-class structure means the total capitalisation is the sum across classes, each at its own price. Multiplying one class's price by the total count across all classes is a common and material error.
- Enter affiliate holdings if you care about the float. The beneficial ownership tables in a proxy statement give you the insider and major holder positions. Without them, the free-float figure simply equals the basic one.
- Set the receipts ratio if you are pricing an ADR. A depositary receipt often represents several underlying shares, and using the receipt price against the ordinary share count multiplies the capitalisation by that ratio.
- Cross-check against a per-share metric. If the EPS calculator and the P/E ratio calculator give you an earnings figure, market cap divided by total earnings should reconcile to the same multiple. If it does not, one of the two share counts is on the wrong basis.
The Formula and How It Is Calculated
The three expressions are:
Market cap = share price × shares outstanding
Free-float cap = share price × (shares outstanding − affiliate-held shares)
Fully diluted cap = share price × (shares outstanding + dilutive instruments)
Where a depositary receipt represents more than one underlying share, the quoted receipt price is divided by the ratio to put it on an ordinary-share basis before any of the above.
Worked example, matching the values the page loads with. A share price of $42.50 against 320 million shares outstanding gives a market capitalisation of 42.50 × 320 = $13,600 million, or $13.60 billion. Affiliates hold 48 million shares, so the free float is 320 − 48 = 272 million shares, which is 85.00% of the total and a free-float capitalisation of 42.50 × 272 = $11,560 million. Adding 12 million dilutive instruments gives 332 million fully diluted shares and a fully diluted capitalisation of 42.50 × 332 = $14,110 million — 3.75% above the headline figure, which is the amount of the company that has already been promised to someone else.
At $13.6 billion the conventional label is large cap, on bands that generally run: below $50 million nano, $50–300 million micro, $300 million to $2 billion small, $2–10 billion mid, $10–200 billion large and above that mega. Those boundaries are convention, they differ between data providers, and they drift upward over time.
Why Market Cap Is Not the Price of the Company
This is the misreading that matters most, and it has two distinct parts.
It only prices the equity. Buying every share does not give you a debt-free business; it gives you the shares and the obligations attached to the company. Two companies with identical operations and identical market caps are not equivalent if one carries $5 billion of net debt and the other holds $5 billion of net cash. That is exactly what enterprise value exists to correct, and it is why acquisition prices are quoted on an enterprise basis rather than a market cap basis.
It extrapolates from the marginal trade. The last price is the price at which a small number of shares changed hands between a willing buyer and a willing seller. Multiplying it across every share assumes that price would hold for all of them, which it demonstrably would not: attempting to buy an entire company drives the price up, and attempting to sell a large holding drives it down. In thinly floated companies the gap between the quoted capitalisation and any realisable value can be enormous, which is why the free-float figure is more informative than the headline for anything involving actually transacting.
FINRA's guide to the financial performance metrics every investor should know sets out how market value, enterprise value and the ratios built on them relate to each other, and it is a reasonable starting point if the distinction is new.
Free Float, Index Inclusion and Public Float
Three related but different concepts share the word float, and confusing them causes real errors.
Free float is the share of the register available to ordinary trading, after removing strategic, government, founder and locked-up holdings. Major index providers weight constituents by float-adjusted capitalisation rather than full capitalisation, precisely so that a fund tracking the index can actually buy its weight. A company with a 20% float and a $50 billion headline capitalisation carries roughly the index weight of a $10 billion company.
Public float is a regulatory measure with a specific definition: the market value of shares held by non-affiliates. In the United States it determines filing status. The SEC's guide to the amendments to the smaller reporting company definition sets out the thresholds — a public float below $250 million, or annual revenues below $100 million with no public float or a float below $700 million — which determine whether a registrant can use scaled disclosure. Where a company sits against those lines changes what it has to file, which is a genuine consequence of a number this page computes.
Tradable float in the everyday sense is smaller still, because index funds and long-term institutional holders rarely trade. This is why a company can have a large free float on paper and a share price that moves sharply on modest volume.
Where the Share Count Goes Wrong
Almost every material market cap error is a share count error, and they cluster into a few patterns.
Stale counts. Share counts change constantly through buybacks, employee issuance and secondary offerings. A count from an annual report is up to a year old, and a company that has repurchased 8% of itself since then has a capitalisation 8% below what the stale figure implies.
Multiple classes. Where Class A and Class B shares exist and only one is listed, using the listed price against the combined count is only correct if the unlisted class is genuinely equivalent in economic terms. Often it is not, and the classes can trade at persistent differences.
Treasury shares. Issued shares and outstanding shares differ by the shares the company holds itself. Treasury stock carries no dividend and no vote and should not be counted, but issued-share figures circulate widely.
Convertibles that are not yet shares. A convertible bond or a warrant is not in the outstanding count until it converts, but it will be. Comparing a basic capitalisation for one company against a diluted one for another rewards the company with more unexercised dilution, which is backwards. Sector context for any of the multiples built on these figures is available in NYU Stern's revenue multiples by sector data set, which reports price-to-sales and EV-to-sales side by side and makes the equity-versus-enterprise distinction concrete.
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See Content Marketing Services Talk to Arb DigitalCommon Mistakes to Avoid
- Using issued shares instead of outstanding shares — treasury stock is held by the company itself, carries no economic interest, and inflates the capitalisation if counted.
- Applying one class's price to all classes — in a dual-class structure the total is the sum of each class at its own price, and the unlisted class may not be economically identical.
- Pricing an ADR against the ordinary share count — if a receipt represents four shares, this overstates the capitalisation fourfold, and the ratio is not always obvious from a quote screen.
- Comparing market caps across companies with different leverage — equity value ignores debt entirely. Use enterprise value when the balance sheets differ materially.
- Treating a size band as a definition — the boundaries are convention, they differ by provider, and they move upward as markets grow, so the same company can be mid cap in one dataset and large cap in another.
Related Free Tools From Arb Digital
Move from equity value to whole-business value with the enterprise value calculator, and build the per-share inputs with the EPS calculator and the P/E ratio calculator. For valuation approaches rather than measurement, see the intrinsic value calculator and the DCF calculator. The dividend yield calculator puts distributions on a per-share basis, the EBITDA calculator supplies the denominator most enterprise multiples use, and the stock profit calculator handles a single position. The rest are in the free online tools hub.
Frequently Asked Questions
It is the share price multiplied by the number of shares outstanding, giving the total market value of a company's equity at the current quoted price. It measures what the equity is priced at, not what the whole business would cost, because it takes no account of debt or cash on the balance sheet.
Market cap prices only the equity. Enterprise value adds net debt and minority interests and subtracts cash, giving a figure that is neutral to how the business is financed. Two companies with identical operations and identical market caps can have very different enterprise values if one is heavily borrowed and the other holds net cash.
It is market capitalisation calculated using only the shares actually available to trade, after removing holdings by founders, directors, controlling families, governments and strategic investors. Major index providers weight their constituents on this basis so that funds tracking the index can realistically buy their required weight.
Use whichever matches what you are comparing against. Diluted counts include options, restricted stock units and convertible instruments that have not yet become shares but very likely will. Comparing one company on a basic count with another on a diluted count rewards the company with more unexercised dilution, which reverses the intended meaning.
From market convention rather than from any regulator or standard. The commonly quoted boundaries run from nano and micro cap up through small, mid, large and mega, but data providers place the lines differently and the thresholds drift upward over time as markets grow. Treat the label as shorthand rather than a category with a fixed meaning.
Calculate each class separately at its own price and add the results. Applying the listed class's price to the total share count is only correct if the other class is economically identical, and in many dual-class structures it is not, since the classes can trade at persistent differences.
Public float is a regulatory measure: the market value of shares held by people who are not affiliates of the company. In the United States it determines a registrant's filing status, including whether it qualifies as a smaller reporting company and can use scaled disclosure, so where a company sits against those thresholds changes what it must file.
No. The quoted price reflects the last few shares that traded, and multiplying it across every share assumes that price would hold for all of them. Attempting to buy an entire company pushes the price up, and acquisitions are typically agreed at a premium and quoted on an enterprise value basis that also accounts for the target's debt.
This tool performs a standard measurement on figures you supply. It is not investment advice and not a recommendation to buy, sell or hold any security. Market capitalisation describes what a market is currently pricing, not what a business is worth and not what any share price will do next. Decisions about your money should involve a licensed financial adviser who is regulated to advise on them.
