Anand Kumar/AI-Generated Image
Summary: Most investors call a stock cheap or expensive without knowing what bet they are agreeing to. Flip the usual valuation exercise around and a P/E turns into something you can actually check. The surprise is how much one overlooked input changes the answer.
Ask most investors why a stock trades at 70 times earnings and the honest answer is usually "because it's a good company." That answer explains nothing. Hundreds of good companies trade at 20 times earnings. A multiple does not measure quality. It measures a bet on how long and how fast that quality keeps compounding, and most investors who call a stock expensive or cheap have never actually worked out what bet they are agreeing or disagreeing with.
Flip the question
The standard way to value a business is a forecast: estimate future cash flows, pick a discount rate, add it all up, and compare the answer to today's price. Every input in that process is a guess, so the output inherits every one of those guesses. Flip the process instead. Start with today's price as a known fact, and work backward to the growth rate that would justify it. This is a reverse DCF, and it turns a wall of assumptions into one checkable number: the growth rate the market is already betting on.
The reverse DCF
A reverse DCF needs just four inputs. The company's current TTM earnings. A discount rate, the annual return you want for taking on stock-market risk instead of something safer, most Indian investors use something around 12 per cent. A terminal multiple, a reasonable P/E the business might still command once its growth phase ends. And a time horizon, how many years you are willing to wait for that growth to play out. Feed those four in, and what comes out is the one number that matters: the growth rate the company needs to deliver, every year, for today's price to make sense.
Same price, three different stories
Here is what that looks like for Sansera Engineering, trading at a P/E of 75, on TTM earnings of ₹350 crore, a market cap of ₹26,156 crore. Hold the required rate of return at 15 per cent and the terminal multiple at 35, a mature business, and change only how many years the growth story gets to play out.
| Time horizon given to grow | Implied growth rate needed every year |
|---|---|
| 5 years | 33.80% |
| 10 years | 24.10% |
| 20 years | 19.40% |
Same company, same price, same discount rate, same terminal multiple. The only thing that changed is how much time the growth gets to compound, and the answer swings from implausible to fairly ordinary. This is the real use of a reverse DCF: not a single verdict, but a way to see exactly how heroic an assumption today's price needs, and over what stretch of time, before you decide whether you believe it.
The quick filter: PEG
A full reverse DCF, run across a few horizons, is the most complete way to check a price. For a faster gut-check without reaching for a calculator, divide the P/E by the expected earnings growth rate instead. This is the PEG ratio, and it answers a narrower question: is this price asking for more growth than the company is actually delivering?
A PEG near one suggests the price and the growth rate broadly agree. A PEG well above one asks for more than the company's own growth currently supports, not proof the stock will fall, but a flag worth investigating. A PEG well below one deserves the opposite question: is the market underestimating the business, or does it know something about next year's growth that has not shown up yet.
As a rule of thumb, a PEG ratio near 1.5 can be considered safe.
What actually moves the multiple, once you own the stock
| Pushes the multiple up | Pulls the multiple down |
|---|---|
| Operating leverage kicks in, profit outgrows revenue | Operating deleverage, fixed costs remain while demand softens |
| Margins expand | Margins compress |
| Capital allocation improves, debt comes down | Capital misallocated into unrelated, debt-funded acquisitions |
| A genuine new growth driver appears | The old growth driver runs out with nothing to replace it |
A multiple does not drift on sentiment alone. It moves because something real has changed in how much growth, margin or durability the market expects, and three different companies show three different triggers.
Shadowfax is the operating-leverage story: delivery volumes scaling past its largely fixed logistics-tech cost base let profit begin outgrowing revenue, and the stock nearly tripling since the IPO in January 2026.
Garware Hi-Tech Films is the margin story: a shift in sales mix toward high-value technical films, paint protection and solar control among them, lifted margins well above its old commodity-film base, and the multiple re-rated with it.
Sansera Engineering is the new-growth-driver story: its push into aerospace and defence components gave the market a fresh growth vector beyond its mature auto-components base, and the stock re-rated on that optionality.
None of these moved on mood. Each moved because something measurable, a cost base finally absorbed, a product mix that shifted, a new business line that opened up, changed what the business could plausibly earn going forward, and the price followed.
Before you act on a P/E
Before acting on any P/E, ask three questions: what earnings growth does this price need, over what time horizon, and would you personally bet on the company delivering it. A five-year story and a twenty-year story can demand wildly different things from the same business. A P/E you cannot translate into a growth rate and a timeframe is not a number you have evaluated. It is a number you have simply accepted.
Also read: The hidden DCF
This article was originally published on October 16, 2026.
Ask Value Research 
New episodes every Friday 
New Process Alert 
Seems like you've uploaded a wrong QR code. Please upload the QR code downloaded from MF Central platform.
