Even a great company can be a bad investment at the wrong price. Comparing metrics like P/E and PEG against a company's own history and its peers helps you judge whether you're paying a fair price or chasing hype.
A $500 share price says nothing about whether a stock is expensive; a $5 share price says nothing about whether it's cheap. What matters is price relative to something — usually earnings. The P/E ratio (price ÷ earnings per share) is the most common starting point: it tells you how many dollars investors are paying today for each dollar of current annual profit.
A high P/E can mean two very different things: genuine excitement about fast future growth, or a stock that's simply overpriced. That's why the PEG ratio (P/E ÷ expected annual earnings growth rate) exists — it adjusts the P/E for how fast the company is actually growing. A PEG around 1.0 suggests the price roughly matches the growth rate; well below 1.0 can suggest a bargain relative to growth; well above 2.0 often suggests the price has run ahead of what the growth justifies.
No ratio works in isolation. The right way to use any valuation metric is comparative: against the company's own historical range (is it trading rich or cheap versus its own past?) and against direct industry peers (a high P/E is normal in some industries and a red flag in others). A ratio with no comparison point is just a number.
Real companies don't come with round numbers, so here's a clean illustrative comparison showing exactly why P/E alone can mislead.
| Metric | Company A | Company B |
|---|---|---|
| Share Price | $75.00 | $75.00 |
| Earnings Per Share | $3.00 | $3.00 |
| P/E Ratio | 25.0 | 25.0 |
| Expected Annual Earnings Growth | 30% | 10% |
| PEG Ratio | 0.83 | 2.50 |
Both companies trade at an identical P/E of 25 — on that number alone, they'd look equally "expensive." But Company A is expected to grow earnings three times faster than Company B. Once growth-adjusted, Company A's PEG of 0.83 looks reasonably priced relative to its growth, while Company B's PEG of 2.50 suggests investors may be paying a much steeper premium for a slower-growing business. Same headline multiple, very different valuation story.
Enter simplified figures — see the P/E ratio, the growth-adjusted PEG ratio, and a rough read on how it looks.
Model: P/E = Share Price ÷ EPS. PEG = P/E ÷ Expected Annual Earnings Growth Rate. PEG below 1.0 is read as potentially cheap relative to growth; near 1.0 as roughly fair; above 2.0 as potentially expensive relative to growth. Always cross-check against peers and the credibility of the growth assumption.
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You've now covered the income statement, balance sheet, cash flow, growth vs dividend styles, and valuation — the full toolkit for reading a company beyond the ticker symbol.