Valuation Multiples (P/E & Friends)
A P/E ratio is a shortcut for “how many years of profit am I paying for?” — a compressed, comparable version of a full valuation.
A full discounted cash flow (last lesson) is powerful but heavy — you can’t run one in your head at a dinner table. Yet investors compare companies in seconds using one little number: the P/E ratio. Is that number a cheat that throws away everything you just learned, or a clever compression of it? And why is a “P/E of 40” a warning to one investor and a bargain to another? Hold the question: what is a P/E ratio actually measuring?
P/E = years of profit you’re paying for
The price-to-earnings (P/E) ratio divides a company’s price by its yearly profit (earnings). A P/E of 20 means you’re paying $20 for every $1 of annual profit — loosely, 20 years of current profit to buy the whole thing. That reframing is the key: a multiple is just a compact way of saying how much you’re paying relative to what the business earns right now. It turns messy prices into one comparable number, so you can line up companies side by side without building a spreadsheet for each.
A multiple is a bet on the future
But why would anyone pay 40 years of profit when another company sells for 8? Because a P/E isn’t really about this year — it’s a compressed expectation of the DCF from last lesson. A high multiple says the market expects profits to grow a lot (so today’s earnings understate the future) or that they’re very safe (low discount rate). A low multiple says the market expects little growth, or sees real risk. So the number bakes in a forecast. This is why “high P/E = expensive” and “low P/E = cheap” are both traps: a high multiple can be a fair price for a fast grower, and a low multiple can be a correct price for a dying business (a “value trap”).
Two companies, opposite stories: • Company A: P/E 8. Cheap-looking — but its profits are shrinking 5% a year. The low multiple is the market pricing in decline, not a gift. • Company B: P/E 35. Expensive-looking — but profits are growing 30% a year. In a few years today’s earnings look tiny, so the high multiple may be justified. The raw number lied; the growth told the truth.
Multiples only compare like with like
Multiples are powerful only in comparison, and only between genuinely similar things. Comparing a software company’s P/E to a bank’s, or a fast grower’s to a mature utility’s, is comparing apples to staplers — different growth, risk, and accounting. That’s why analysts compare a company to its own history and to close peers (comparables). And P/E has cousins for when earnings are a poor measure: price-to-sales for young companies with no profit yet, price-to-book for asset-heavy ones. Same idea every time — price relative to some fundamental — and the same rule: the multiple is a question (“what is the market assuming?”), not an answer.
A P/E ratio is the price tag on a rental property expressed as “years of rent.” If a building costs 20 years of its current rent, that’s your quick read on expensive-or-cheap. But two buildings at “20 years” aren’t equal: one sits in a booming neighborhood where rents will climb (cheap in hindsight), the other in a declining town where rents will fall (the 20 was optimistic). The number is a fast, comparable starting point — but you still have to ask what’s going to happen to the rent. The multiple hands you the question; the future writes the answer.
Using a multiple without being fooled: 1. A stock trades at a P/E of 15. First read: you’re paying ~15 years of current profit. 2. Compare, don’t judge alone: its close peers average a P/E of 25, and its own 10-year average is 22. 3. So it’s cheap relative to its peers and history — now ask why. Slowing growth? A scandal? A bargain? 4. The multiple didn’t tell you to buy or sell; it pointed a spotlight at the exact question worth researching. That’s all a multiple is for.
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