What Is Valuation?
Valuation is the process of estimating and comparing a company's worth. Just as you would compare apartment prices in similar neighborhoods, investors compare a stock's price relative to its earnings, assets, or cash flow to judge whether it is cheap or expensive. The key insight is that valuation metrics are comparison tools, not buy signals.
The denominators (earnings, book value) come from financial statements. For market-wide overvaluation debates, also see the Buffett Indicator.
P/E Ratio — How Many Times Earnings?
P/E (Price-to-Earnings) = Stock Price ÷ EPS (Earnings Per Share — how much the company earned per share over the past year).
Numeric example
Stock price $100, trailing EPS $5 → P/E = 100 ÷ 5 = 20x.
Rough interpretation: if earnings stayed flat forever, it would take 20 years to recoup your investment. In practice, earnings grow or shrink, and dividends and buybacks change the picture.
If Company A trades at P/E 15 and Company B at P/E 30 in the same industry, B is “more expensive per dollar of earnings” — but B may justify the premium with faster growth.
- Growth stocks (tech, biotech): P/E 30–50 can reflect genuine growth expectations
- Mature / slow-growth companies: P/E 10–15 is common
- Loss-making companies: EPS is negative, so P/E is meaningless — use Price/Sales (P/S) instead
P/B Ratio — How Many Times Book Value?
P/B (Price-to-Book) = Stock Price ÷ Book Value Per Share (total assets minus liabilities, divided by shares outstanding).
Example: Stock price $50, book value per share $25 → P/B = 2. The stock trades at twice its accounting net worth. A P/B below 1 means the market values the company below its book value — but this is often a warning sign of declining business quality, not a free lunch.
P/B is most useful for asset-heavy sectors like banks and manufacturing. For software or brand-driven companies, enormous intangible assets don't appear on the balance sheet, making P/B misleading on its own.
EV/EBITDA — Including Debt
Enterprise Value (EV) ≈ Market cap + net debt. It represents the total price to acquire the entire business, debt included. EBITDA is operating profit before interest, taxes, depreciation, and amortization — a rough proxy for cash generation.
Why it matters: If Company A has no debt and Company B carries heavy debt, their P/E ratios may look similar while B is actually far more expensive on an enterprise basis. EV/EBITDA is widely used in M&A and private equity, and is useful for individual investors comparing leveraged companies.
PEG — Adjusting for Growth
PEG ≈ P/E ÷ Expected Earnings Growth Rate (%). Example: P/E 30, expected growth 15% → PEG = 2. A PEG near 1 is often cited as “fairly valued for its growth.” The caveat: growth estimates are frequently wrong, so PEG inherits those errors.
Reading P/E and P/B Together
High P/E + High P/B — growth and optimism are heavily priced in; overvaluation risk
Low P/E + Low P/B — looks cheap, but may be a “value trap” (declining business)
High P/E + Normal P/B — strong profitability but trading at a premium to assets
Rising rates — higher discount rates compress growth-stock P/E ratios (see rates guide)
Beginner Checklist
- List P/E and P/B for 3–5 peers in the same sector
- Check whether the last 4 quarters of EPS include one-time gains (asset sales, etc.)
- Look at debt — is the company expensive on an EV basis?
- Sanity-check PEG: is the P/E absurdly high relative to realistic growth?
- Never bet everything on “cheap” — size positions with a portfolio plan and checklist
Common Mistakes
Buying only low-P/E stocks
The business may be structurally declining. Low P/E can be a value trap.
Comparing across industries
A bank's P/E and a software company's P/E are not comparable. Always compare within the same sector.
Using P/E for loss-making companies
A negative denominator breaks the ratio entirely.
Acting on a single moment's numbers
Combine with earnings season, rates, and industry context.
Timing index ETF purchases with P/E
For core DCA positions, execution consistency matters more than valuation timing.
Connection to Value Investing
Graham and Buffett's framework is “buy below intrinsic value.” P/E and P/B are only a slice of that picture. For the full philosophy, read the Value Investing Guide; for chart-based supplementation, see Technical Analysis.
For a market-wide valuation gauge, the Buffett Indicator (total market cap / GDP) gives a broad picture. Do not confuse it with individual-stock P/E.
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