AlphaScope Note · Connected valuation metrics guide
P/E P/B ROE Explained: How EPS and ROIC Connect
This P/E P/B ROE guide connects company profit and equity with per-share figures, market multiples, and capital efficiency instead of treating each ratio as an isolated formula.
The short answer
A low P/E is not automatically cheap, a P/B below 1 is not automatically safe, and a high ROE does not guarantee high-quality earnings. Before judging a ratio, identify its numerator and denominator, test whether earnings are repeatable, and ask whether leverage inflated the return.
What each metric does
Follow the money before reading the price tags
EPS and BVPS convert company-wide numbers into the amount attributable to one share. P/E and P/B show how much the market pays for those per-share figures. ROE and ROIC measure how effectively capital produces profit.
Profit earned per share
Net income divided by weighted-average shares.
Price as a multiple of EPS
Share price divided by EPS.
Price as a multiple of BVPS
Share price divided by book value per share.
Return earned on equity
Net income divided by average equity.
Return on capital in the business
NOPAT divided by average invested capital.
Where P/E begins
EPS turns company profit into one share’s portion
A company may earn $1 million in a year, but that total says little about one share until we know how many shares participated in those earnings. With 1 million weighted-average shares, EPS is $1.
Why weighted-average shares matter
Suppose 1 million shares were outstanding from January, then another 1 million shares were issued in October. The new shares existed for only three months. Dividing the entire year’s profit by the 2 million year-end shares would overstate how long those new shares participated.
$1.5m net income ÷ 1.25m weighted shares$1.20 EPS
$1.5m net income ÷ 2m year-end shares$0.75Simple calculation ignores timing
The price attached to earnings
P/E shows how much the market pays for $1 of earnings
If a share trades at $20 and EPS is $2, the P/E ratio is 10. A common shorthand is that the price equals roughly ten years of current annual earnings. That does not mean your investment will automatically be repaid in ten years. A company does not distribute all earnings as cash, and future earnings can rise or fall.
It may look cheap because earnings are near a peak
In cyclical industries, temporarily high EPS can push P/E down just before profits normalize.
It may look expensive because growth is priced in
A higher multiple may reflect expectations for durable growth, lower business risk, or strong capital efficiency.
Why the same company can show different P/E ratios
It is based on actual results but may react slowly to a change in the business.
It looks ahead, but the ratio changes whenever analyst estimates change.
Before comparing P/E ratios, align the share-price date, earnings period, consolidated or standalone basis, and treatment of one-off gains and losses.
The price attached to book equity
P/B is the multiple the market assigns to shareholders’ book value
Read the diagram in three steps. Subtract liabilities from assets to find shareholders’ equity. Divide equity by the share count to convert it into BVPS. Finally, compare the share price with BVPS to calculate P/B.
The accounting amount left for shareholders after liabilities.
The company-wide book equity translated into a per-share figure.
The market price and book value per share are at the same level.
P/B 1×Price equals BVPSThe market pays $1 for $1 of book equity
P/B 1.5×Price is 50% above BVPSProfitability, growth, or intangible strengths may be reflected
P/B 0.7×Price is 30% below BVPSWeak returns, asset-quality concerns, or future losses may be reflected
Banks, insurers, and capital-intensive businesses
Asset quality and equity may be relatively important to explaining business value.
Software, brands, and human capital
Internally developed intangible advantages may not be fully captured in book value.
Efficiency of shareholders’ capital
When ROE is high, break down how it became high
If a company earns $1 million on $10 million of average equity, ROE is 10%. But the quality and risk differ depending on whether the return came from strong margins and operations or from heavier borrowing.
The hypothetical company above has $10 million in revenue, $1 million in net income, $8 million in average assets, and $5 million in average equity. The three components are calculated as follows.
The company keeps $10 of net income from every $100 of sales.
Each $1 of assets produces $1.25 of annual sales.
Each $1 of equity supports $1.60 of assets; the remainder is funded mainly by liabilities.
Algebraically, this is (net income ÷ revenue) × (revenue ÷ assets) × (assets ÷ equity). Revenue and assets cancel, leaving net income ÷ equity, or ROE. The decomposition shows whether ROE came from margins, asset use, or leverage.
The same 20% ROE can have a different quality
Profitability and asset efficiency support the return, with relatively modest leverage.
Profitability is weaker, but high leverage lifts ROE to the same headline number.
When ROE is high, also review debt ratios, net debt, interest coverage, and operating cash flow. Be cautious when unusually small or negative equity makes ROE extreme or unusable.
The key relationship
The P/E P/B ROE relationship: P/E × ROE = P/B
Using consistent periods and definitions, ROE can be expressed on a per-share basis as EPS ÷ BVPS. Multiply P/E by ROE and EPS cancels, leaving price ÷ BVPS—or P/B. Use ROE as a decimal in the multiplication: 10% is 0.10.
The matching EPS terms cancel.
The company may hold substantial equity without producing enough profit, or profitability may be deteriorating.
The market may assign a low multiple because growth expectations are weak or business risk and the cost of capital are high.
Interactive relationship calculator
What happens to the other metrics when one number changes?
Change the hypothetical company’s inputs. A change in price moves P/E and P/B; a change in net income moves EPS, P/E, and ROE together. The formulas are intentionally simplified to make the relationships visible.
About $0.5m of potential value creation on invested capital
The company earns $2.00 per share. The market pays 10× those earnings and 1× book value per share.
Actual published metrics may differ because providers use specific definitions for attributable income and equity, beginning-and-ending averages, corporate-action adjustments, market-price dates, and share counts. The value-creation estimate is the educational approximation (ROIC − WACC) × invested capital, not accounting profit.
Efficiency of all operating capital
ROIC looks at the business engine funded by debt and equity
ROE uses shareholders’ equity in its denominator. ROIC instead asks how much after-tax operating profit the capital committed to operations produced. That makes ROIC useful when leverage may be flattering ROE.
Equity supplied by shareholders and interest-bearing debt supplied by creditors are converted into equipment, inventory, and working capital. ROIC measures how efficiently all capital tied to operations generates after-tax operating profit, regardless of where the funding came from.
equipment, inventory, and working capital
Compare ROIC with WACC
A 10% ROIC means $100 invested in operations produced about $10 of after-tax operating profit. An 8% WACC means the shareholders and creditors providing that $100 collectively require about $8 of return. A positive 2-percentage-point spread suggests the business earned more than its cost of capital.
Signals that can mislead
What to check before calling a ratio low or high
A multiple describes a result, not its cause. The events below can move a numerator or denominator sharply, so investigate the financial statements and notes even when a ratio looks attractive.
A negative P/E is not a cheap P/E
When EPS is negative, comparing P/E multiples loses meaning. Treat the ratio as not meaningful rather than “below zero and cheap.”
An asset sale can inflate EPS and ROE
Compare reported profit with normalized profit and operating cash flow.
Beware a low P/E at peak earnings
Recheck the multiple using normalized earnings or a multi-year average.
EPS can move when only the share count changes
Separate profit growth from a lower denominator caused by share repurchases.
Compare basic and diluted EPS
Convertible securities and options can increase future share count and reduce per-share value.
Do not rank unlike businesses on one line
Banks, manufacturers, and software firms have different capital and accounting structures. Compare close peers.
Separate an unusual year from a structural trend.
Compare similar business models and accounting economics.
See where valuation and capital efficiency sit within the industry.
A practical reading sequence
Use this order when you open a company page
Following how each number is produced reduces the blind spots created by judging a single ratio in isolation.
Identify repeatable operating profit and one-off items
Separate profit growth from dilution or buyback effects
Align periods, then compare history and peers
Find whether margin, turnover, or leverage changed
Test whether operating returns exceed funding costs
- Did I compare the company with its own historical results?
- Did I compare close peers with similar business models?
- Did I separate one-off items and cyclical peaks or troughs?
- Did I review debt, dilution risk, and changes in share count?
- What evidence suggests today’s numbers can persist?
Frequently asked questions
Quick answers to the confusing parts
What P/E ratio counts as undervalued?
There is no universal cutoff. Growth, business risk, capital costs, and the point in the cycle differ. Compare the company with its own history and close peers, then investigate why the multiple is low.
Does P/B below 1 mean the stock trades below liquidation value?
No. BVPS is accounting book value, not guaranteed sale value. Review asset quality, unrecorded obligations, and the risk that future losses reduce equity.
What is a good ROE?
It depends on the industry and capital structure. Persistence, the cost of equity, and whether margin, turnover, or leverage produced the return matter more than one universal percentage.
Why does P/E × ROE differ from P/B on a data screen?
The identity is exact when EPS, BVPS, and ROE use consistent dates and definitions. Published figures may mix period-end equity, average equity, trailing earnings, and weighted-average shares.
Should I focus on ROE or ROIC?
They are complements. ROE measures the return from the shareholder’s perspective; ROIC measures the return generated by all capital committed to operations. Companies with heavy debt or capital needs especially warrant both measures and a cost-of-capital comparison.
Primary references
Sources for definitions and calculation conventions
- IFRS Foundation: IAS 33 Earnings per ShareBasic and diluted EPS and weighted-average shares
- Korea Exchange investment-indicator calculation guideDetailed KRX conventions for EPS, BPS, P/E, P/B, and ROE
- Korea Exchange Corporate Value-Up guideline commentaryP/B decomposition, DuPont analysis, and ROIC versus WACC
- Korea Exchange sector investment indicatorsPeer and sector comparisons for P/E, P/B, and ROE