When a company creates new shares, every existing share owns a smaller piece of it. Whether that costs you anything depends on what the company gets for those shares.
A smaller slice
Start with a company split into 100 shares. You own 10, so you own 10 percent. Now the company creates 25 new shares and sells them. There are 125 shares, you still hold 10, and your stake has fallen to 8 percent. That drop is dilutionThe shrinking of each existing share’s slice of a company when new shares are created..
New shares appear in several ways. A company can sell them for cash. It can hand them over to pay for another business; most mergers in the 1990s were paid this way.3 It can also promise shares later, through options, warrants and convertible securities, which turn into new shares when their holders exercise or convert them.4
Smaller is not automatically worse
Put numbers on it. Say the company is worth $1,000 before the sale, or $10 a share. If it sells the 25 new shares at $10 each, it collects $250. The company is now worth $1,250, spread over 125 shares: still $10 a share. Your slice shrank, but the pie grew by exactly what the new owners paid, so your 10 shares are worth what they were.
Now say it sells them at $6. It collects only $150, the company is worth $1,150, and each share is worth $9.20. The 80 cents per share did not vanish; it moved to the buyers, who paid less than their slice was worth.
Figure 1: Same dilution, two outcomes. Selling 25 new shares cuts your stake from 10% to 8% either way. At a fair price each share keeps its $10 of value; sold cheaply, each share drops to $9.20. Illustrative numbers, no real company.
So the question about dilution is never just “how many new shares?” It is “at what price, and what does the money do next?” Cash that goes into a project worth more than it cost can leave each share worth more, even with a smaller slice. Cash that is spent poorly leaves each share worth less. The same logic covers paying for a business in stock: you are trading part of your company for theirs, and the trade is good only if what arrives is worth what was given up.
Why the price often falls anyway
In theory, with efficient markets and investment plans held fixed, selling new shares at a fair price should not move the share price.1 In practice it often does. A classic study of 531 US share offerings from 1963 to 1981 found that announcements of new share sales by industrial companies were followed, on average, by a drop of about 3 percent over two days.1 The value lost was a substantial fraction of the money being raised.1
Two explanations fit those results. One is a signal: managers know more than outside investors, and they are more willing to sell new shares when they believe the price is generous, so investors read a sale as a hint that the shares may be overpriced.2 The other is that extra supply pushes the price down.1 These are averages from decades-old data, not a rule for any single company.
Dilution that has not happened yet
Options, warrantsA right to buy new shares from the company at a fixed price before a set date. and convertibles are dilution waiting in the wings. That is why the international accounting standard for earnings per share requires a second figure, diluted earnings per share, which assumes those instruments are converted or exercised.4 Watch for one kind in particular: convertibles whose conversion price floats with the market, so the lower the share price falls, the more new shares they create.5
How to read it
When a company raises money, look past the dollar amount to the share count. Compare how fast shares outstanding grow with how fast the things they own grow, such as cash, revenueA signed order is good news, but it is not revenue yet. or customers per share. Check the fully diluted count, not just today’s. And ask the two questions: was the price fair, and what will the money buy? This is a way to read the numbers, not a verdict on any company.
Sources
P. Asquith and D. W. Mullins Jr., “Equity issues and offering dilution,” Journal of Financial Economics 15, 61 (1986). DOI: 10.1016/0304-405X(86)90050-4. (Theory: with close substitutes, efficient markets and fixed investment policies, share price should not depend on the number of shares sold; 531 registered US offerings, 1963 to 1981; average two-day announcement excess return of about -3.0% for primary industrial offerings, -2.7% for the full sample; announcement-day loss a substantial fraction of the proceeds; consistent with a negative-signal hypothesis and with downward-sloping demand for shares. Read from a full-text copy of the journal article.) ↩
S. C. Myers and N. S. Majluf, “Corporate financing and investment decisions when firms have information that investors do not have,” Journal of Financial Economics 13, 187 (1984). NBER Working Paper 1396, DOI: 10.3386/w1396. (Managers know more than investors; when management acts for existing shareholders, the decision to issue stock causes the price to fall; issuing only when stock is overvalued.) ↩
G. Andrade, M. Mitchell, and E. Stafford, “New evidence and perspectives on mergers,” Journal of Economic Perspectives 15(2), 103 (2001). DOI: 10.1257/jep.15.2.103. (Mergers in the 1990s were mostly stock swaps. Checked from the published abstract.) ↩
IFRS Foundation, IAS 33 Earnings per Share, standard summary, ifrs.org (accessed October 20, 2026). (Potential ordinary shares include convertibles, options and warrants; basic and diluted EPS must be presented with equal prominence; dilution defined as the potential reduction in EPS from assumed conversion or exercise.) ↩
US Securities and Exchange Commission, Investor.gov, “Convertible Securities” (accessed October 20, 2026). (Dilution as the reduction in earnings per share and proportional ownership when convertibles convert; market-price-based conversion formulas issue more shares as the price falls.) ↩
