EPS: Basic vs Diluted Earnings per Share

Introduction

Earnings per share (EPS) is the most quoted earnings figure for public companies: analysts forecast it, boards set targets on it, and the price-to-earnings multiple is built on it. Yet almost every US public company reports two versions, because any company with stock options, restricted stock or convertible securities must. Basic EPS divides earnings by the shares actually outstanding. Diluted EPS divides earnings by a larger number that includes shares which do not yet exist but could, if employees exercised options, restricted stock vested or bondholders converted. Microsoft reported basic EPS of $13.70 and diluted EPS of $13.64 for fiscal 2025, a small gap; at companies with large option programs or convertible bonds, the gap can be far wider.

Both figures are governed by Accounting Standards Codification (ASC) Topic 260, and both depend on a weighted-average share count rather than the number of shares at year end. The calculation is mechanical once the rules are clear, but the rules contain judgments that matter to bankers: which securities are dilutive, which method applies to each, and how the reported diluted share count differs from the fully diluted share count used to compute a company's equity value.

Basic EPS starts from the earnings available to common shareholders: net income attributable to the parent, less dividends on preferred stock, which rank ahead of common shareholders. That figure is divided by the weighted average of common shares outstanding during the period:

The weighted average reflects how long each share was outstanding. Consider a company that starts the year with 1,000 shares, issues 200 new shares on April 1 and buys back 100 shares on October 1:

With $2,250 million of net income available to common shareholders, basic EPS is $2.00. Using year-end shares instead would give $2.05, overstating earnings per share: it treats the 100 repurchased shares as retired for the whole year rather than the last three months, an error larger than the one it makes in counting the 200 new shares for twelve months instead of nine.

Weighted-average shares outstanding

The average number of common shares outstanding during a period, with each share weighted by the fraction of the period it was outstanding. It is the denominator of basic EPS and, with potential shares added, of diluted EPS.

Two refinements apply to the share count. Stock splits and stock dividends are applied retroactively to all periods presented, so a two-for-one split doubles the share count for prior years as well, keeping EPS comparable. And when a company has participating securities, such as certain preferred stock or unvested awards that receive dividends alongside common shares, earnings are allocated between the classes under the two-class method before EPS is calculated.

The two-class method can move EPS materially. Suppose a company earns $1,000 million, has 900 million common shares and 100 million participating preferred shares that receive the same dividend per share as common stock, and pays $0.50 per share to both classes. Of the $500 million paid out, common holders receive $450 million and preferred holders $50 million; the $500 million retained is allocated in proportion to shares, $450 million to common and $50 million to preferred. Earnings attributable to common shareholders are therefore $900 million, and basic EPS is $1.00, not the $1.11 that dividing all earnings by common shares alone would suggest.

The presentation of businesses being sold or spun off, and why their per-share results are shown separately, is covered in discontinued operations. The repurchase in the example above also shows why buybacks lift EPS gradually rather than all at once: shares bought late in the year reduce the weighted average only for the months that remain, a timing effect explained alongside the accounting for repurchased shares in share repurchases and treasury stock.

Shares That Count Before They Are Issued

A few categories of shares enter basic EPS earlier, or later, than their legal issue date suggests. Shares issuable for little or no cash, such as warrants with a nominal exercise price, are treated as outstanding once the conditions for issuing them are met, because the holder is economically a shareholder already. Unvested restricted stock, by contrast, is legally issued but excluded from basic EPS until it vests, and enters diluted EPS instead. Shares that will be issued to the sellers of an acquired business once a target is met are left out of basic EPS until the condition is satisfied. Each of these choices moves the denominator, and the EPS note explains how the company has treated them.

Why Quarterly EPS Does Not Add Up to Annual EPS

Quarterly EPS is calculated on each quarter's own weighted-average share count, and dilution is tested quarter by quarter. Annual EPS uses the weighted average for the full year and tests dilution against year-to-date earnings, so a security left out of a loss-making quarter can still count in the annual figure. When the share count changes during the year, or a security is dilutive in some quarters and anti-dilutive in others, the four quarterly figures will not sum exactly to the annual figure.

Analysts building annual estimates from quarterly ones, or deriving a fourth quarter by subtraction, should recompute EPS from earnings and shares rather than adding per-share figures, and the same goes for a last-twelve-months (LTM) figure assembled from four quarterly reports. Earnings add up across quarters; per-share figures do not.

Diluted EPS answers a hypothetical question: what would EPS have been if every instrument that could become common stock, and would reduce EPS by doing so, had been converted or exercised? These potential common shares include stock options, restricted stock units, warrants, convertible debt, convertible preferred stock and shares that will be issued if performance conditions are met. For most large companies the main source is employee equity compensation, whose grants, vesting and expense are explained in stock-based compensation accounting; for companies that have issued convertible bonds, conversion can add far more shares than any employee plan.

Diluted EPS

Earnings per share calculated as if all dilutive potential common shares, such as options, restricted stock units, warrants and convertible securities, had been issued, using the treasury stock method for options and similar instruments and the if-converted method for convertibles. Securities that would increase EPS are excluded.

The hypothetical is applied instrument by instrument, not to the capital structure as a whole. Each issue of potential shares is tested on its own for whether it would lower EPS, and each type changes the calculation differently: some add shares only, while others also add earnings back to the numerator. A company with options, performance awards and two convertible bonds therefore runs at least four separate calculations before it reports a single diluted figure. Each type has its own method:

The Treasury Stock Method

Options and warrants bring cash into the company when exercised, and the treasury stock method assumes that cash is used to buy back shares at the average market price for the period. Only the net new shares enter the denominator. Suppose employees hold options on 100 million shares with an exercise price of $20, and the average share price for the year was $40. Exercise would bring in $2,000 million, enough to repurchase 50 million shares at $40, so the net dilution is 50 million shares:

Options with an exercise price above the average share price are out of the money and are excluded, because exercising them would produce fewer shares than the buyback could absorb. For restricted stock units, which have no exercise price, the assumed proceeds consist of the compensation cost not yet recognized, so unvested units create somewhat less dilution than their headline number.

Treasury stock method

The method used in diluted EPS for options, warrants and similar instruments. It assumes the instruments are exercised and the proceeds, including any unrecognized compensation cost, are used to repurchase common shares at the average market price, so only the net increase in shares is added to the denominator.

The If-Converted Method

Convertible bonds and convertible preferred stock work differently, because conversion removes a cost rather than bringing in cash. The if-converted method assumes conversion at the start of the period, or at issuance if later: the shares that would be issued are added to the denominator, and the interest or preferred dividends that would no longer be paid are added back to the numerator, after tax in the case of interest. Since Accounting Standards Update (ASU) 2020-06, US GAAP requires the if-converted method for convertible instruments and presumes settlement in shares when an instrument can be settled in cash or shares, which removed an earlier approach that let many issuers show less dilution. How the bonds themselves are carried on the balance sheet after that change is covered in convertible debt accounting.

Continuing the example, suppose the company also has $1,000 million of convertible notes paying 4% interest, convertible into 40 million shares, with a 25% tax rate. Conversion would add $30 million of after-tax earnings ($40 million of interest less $10 million of tax) and 40 million shares. The full walk from basic to diluted EPS looks like this:

Diluted EPS of $1.88 is about 6% below basic EPS. The ordering matters: instruments are added in sequence from the most dilutive, measured by the earnings added per share added, to the least. Options add shares and no earnings, so they always come first.

Anti-Dilution and Net Losses

An instrument is anti-dilutive if including it would raise EPS, and anti-dilutive securities are excluded. A convertible whose after-tax interest per conversion share exceeds EPS, or options that are out of the money, fall into this category. Companies disclose the number of anti-dilutive securities excluded, which is worth reading, because they can become dilutive quickly if the share price or earnings change.

The rule produces an apparent oddity for loss-making companies. When a company reports a net loss from continuing operations, adding shares would make the loss per share smaller, so every potential share is anti-dilutive and diluted loss per share equals basic loss per share. A company with a large option overhang can therefore report the same basic and diluted figures in a loss year and a sudden gap when it returns to profit.

Performance Shares and Other Contingent Awards

Contingently issuable shares, such as performance share units that vest only if earnings or share price targets are reached, follow a rule of their own. They enter diluted EPS only if the conditions would be satisfied if the end of the reporting period were the end of the contingency period. A performance award tied to a three-year earnings target is therefore excluded while the company is tracking below the target and included once current results would meet it, which can make diluted share counts step up in a strong year.

Bankers use EPS directly in three places. The price-to-earnings (P/E) multiple compares share price with EPS, almost always on a diluted basis and on forward estimates. Accretion and dilution analysis asks whether an acquisition raises or lowers the buyer's EPS, and is covered in the Valuation guide's article on accretion and dilution analysis. And share repurchase analysis asks how much a buyback will lift EPS, which depends on the price paid and the earnings forgone on the cash used.

The reported diluted share count is not the same as the share count bankers use to compute equity value, and the difference matters. Reported diluted EPS uses weighted-average shares and the average share price for the period. Equity value uses the shares outstanding on the latest date available, from the cover page of the most recent filing, plus the dilution from options, restricted stock and convertibles calculated at the current share price, or at the offer price in an acquisition. A company whose share price has risen sharply since the period ended will have more dilution at today's price than its reported diluted EPS suggests. The full calculation is set out in the Valuation guide's article on equity value and how to calculate it.

When a Buyback Is Accretive to EPS

Whether a repurchase raises EPS depends on a comparison between two yields. Suppose a company earns $1,000 million on 500 million shares, so EPS is $2.00 and, at a share price of $60, the price-to-earnings ratio is 30x. It spends $1,500 million of cash that was earning 4% before tax to buy back 25 million shares. The forgone interest is $60 million before tax, or $45 million after a 25% tax rate, so net income falls to $955 million while shares fall to 475 million. EPS rises to about $2.01, barely accretive.

The rule behind the arithmetic is that a buyback is accretive when the earnings yield on the shares bought, the inverse of the P/E ratio, here about 3.3%, exceeds the after-tax cost of the cash used, here 3.0%. A company trading at a high multiple and funding buybacks with debt can find repurchases dilutive; one trading at a low multiple with idle cash finds them strongly accretive. Stock-based compensation pushes the other way throughout, adding shares every year as awards vest and options are exercised, so net dilution from compensation is a cost a buyback program must offset before it reduces the share count at all.

Fully Diluted Shares at Today's Price

The difference between reported and current dilution is easiest to see with numbers. Take the technology company in the example above, with 500 million basic shares and options on 60 million shares at an average strike of $30. Reported diluted EPS used the year's average price of $90, giving 40 million net new shares. If the share price today is $120, the treasury stock method at today's price gives 45 million net new shares, so the fully diluted count for equity value is 545 million rather than the 540 million implied by the EPS calculation. In an acquisition at a premium, the calculation is done at the offer price, and the gap widens further.

The face of the income statement shows basic and diluted EPS and usually the weighted-average share counts. The EPS note goes further, reconciling the numerator and denominator of basic EPS to those of diluted EPS, showing the incremental shares from each type of instrument, and disclosing the securities excluded as anti-dilutive. Microsoft's fiscal 2025 income statement shows 7,433 million weighted-average basic shares and 7,465 million diluted shares, so dilutive securities added only about 32 million shares, about 0.4%, which is why its two EPS figures are so close.

Convertible instruments deserve extra attention because their accounting and their dilution are both set out in the debt note, and the conversion terms decide when they move from anti-dilutive to dilutive.

A careful reading of the EPS note, the equity compensation note and the debt note together, as described in how to read a 10-K and 10-Q, gives a complete picture of every share that exists and every share that could, which is the starting point for any per-share analysis a banker builds.