Accretion / dilution
By Michael Song · Wharton MBA · ex-Greenhill · investment banking interview coach
4 min read · updated June 29, 2026
Accretion/dilution answers one blunt question the acquirer's CFO and board care about: does this deal raise or lower our earnings per share? If pro-forma EPS (the combined company's EPS after the deal) goes up, the deal is accretive. If it goes down, it's dilutive. That's the whole test: an EPS sensitivity, run before anyone gets excited about strategic logic.
The build is a sequence, and interviewers want the sequence: combine the two companies' net incomes, add after-tax synergies, subtract the after-tax cost of financing the deal, then divide by the new pro-forma share count. Compare that to the acquirer's standalone EPS.
Cash vs. stock: what changes the answer
The financing decides a lot, because each source has a different "cost" that eats into combined earnings:
- Cash: funded off the balance sheet or new debt. The cost is the forgone interest on the cash or the after-tax interest on the new debt. With rates low relative to earnings yields, cash deals usually come out accretive.
- Stock: the acquirer prints new shares to pay the seller. The cost is dilution of the share count. Whether it helps or hurts depends entirely on the relative P/E ratios.
- Debt: like cash, the cost is after-tax interest. Cheaper than equity, so it tends toward accretive.
The P/E rule of thumb
For an all-stock deal, there's a shortcut you should know cold:
- Acquirer's P/E higher than the target's → the deal is accretive.
- Acquirer's P/E lower than the target's → the deal is dilutive.
The intuition: a high-P/E acquirer is issuing "expensive" shares to buy "cheaper" earnings, so each new share brings in more income than it costs, and EPS rises.
Two traps here. First, candidates apply the P/E rule to cash deals. It's an all-stock heuristic only, and a cash deal's accretion hinges on interest rates and yields, not relative P/Es. Second, and bigger: people treat "accretive" as "good deal" and "dilutive" as "bad deal." Accretion/dilution measures EPS impact. It says nothing about whether the deal creates value. A company can do an accretive acquisition that destroys value (overpaying for declining earnings) or a dilutive one that's strategically brilliant. Don't conflate the EPS arithmetic with value creation.
A worked example
Acquirer earns $1,000 of net income on 1,000 shares → $1.00 EPS. It buys a target earning $200 of net income, all in stock, issuing 150 new shares. Ignore synergies and assume an all-stock deal with no financing cost.
Pro-forma net income is 200 = $1,200; pro-forma shares are 1,000 + 150 = 1,150. Pro-forma EPS = $1,200 / 1,150 = $1.04. EPS rose from $1.00 to $1.04, so the deal is accretive by about 4%. (Consistent with the rule of thumb: the acquirer's earnings yield was richer than the price it paid for the target's earnings.)
The reason a CFO runs this first is optics and incentives: public-market investors and management comp both key off EPS, so a dilutive deal is a hard sell to the board even when it's strategically sound. The banker's job is to know the EPS answer and be able to separate it from the value question, because the two genuinely can point in opposite directions.
Walk the pro-forma EPS build in a fixed order every time: combine net incomes → add after-tax synergies → subtract after-tax financing cost → divide by the new share count → compare to standalone EPS. Saying it as a clean sequence, with the after-tax adjustments called out, is what reads as fluency in a merger model, far more than getting the last decimal right.
Glossary
New to the lingo? Every term used above, in plain English.
- EPS (Earnings Per Share)
- A company’s profit divided by its number of shares. It is the per-share slice of earnings that each shareholder owns.
- Pro forma
- A combined view of two companies as if they had already merged. Pro forma EPS is the merged company earnings per share, used to test whether a deal helps or hurts.
- Accretion
- A deal is accretive when it raises the buyer’s earnings per share (EPS).
- Dilution
- A deal is dilutive when it lowers the buyer’s earnings per share (EPS).
- Net income
- A company profit after all expenses, interest, and taxes are taken out. It is the bottom line of the income statement, also called earnings.
- Synergies
- The extra value two companies expect to create by combining, usually cost savings or added revenue that neither could achieve alone.
- P/E ratio (Price to Earnings)
- A company share price divided by its earnings per share. It shows how many dollars investors pay for each dollar of profit, and lets you compare how expensive stocks are.
Frequently asked
- What makes a deal accretive or dilutive?
- A deal is accretive if pro-forma EPS rises above the acquirer's standalone EPS, and dilutive if it falls. You combine the two companies' net incomes, add after-tax synergies, subtract the after-tax cost of financing, then divide by the new pro-forma share count. That is the whole test.
- In an all-stock deal, how do you tell if it is accretive or dilutive?
- Compare the two P/E ratios. If the acquirer's P/E is higher than the target's, the all-stock deal is accretive; if it is lower, it is dilutive. A high-P/E buyer issues expensive shares to buy cheaper earnings, so each new share brings in more income than it costs, and EPS rises.
- Does accretive mean it is a good deal?
- No. Accretion measures only the EPS impact, not whether the deal creates value. A company can run an accretive acquisition that destroys value by overpaying for declining earnings, or a dilutive one that is strategically brilliant. Never confuse the EPS arithmetic with a verdict on value; they can point in opposite directions.
Make it stick
Drill what you just learned