P/E Ratio Explained: When Is a Stock Actually Expensive?

Every stock screening app displays the P/E (Price-to-Earnings) Ratio. It is the most commonly cited metric on Dalal Street, yet it is routinely misunderstood by retail investors.

What the Math Actually Means

If a stock trades at ₹500 and its annual profit per share is ₹25, its P/E ratio is 20x.

​In plain English: You are paying ₹20 for every ₹1 of profit the business currently generates. Alternatively, it tells you that if the company’s profits remain flat, it will take 20 years of earnings to recoup your purchase price.

​Why a Low P/E Isn't Always "Cheap"

​A common rookie mistake is assuming a stock with a P/E of 8 is cheap while a stock with a P/E of 40 is expensive.

• The Value Trap (Low P/E): Heavily indebted companies, businesses facing technological obsolescence, or cyclical sectors at the peak of their boom often trade at single-digit P/Es. The market is pricing in declining future profits.

• The Growth Premium (High P/E): High-quality consumer or technology franchises consistently reinvest capital at high rates of return. Investors willingly pay 45x or 50x earnings because profits are expected to compound rapidly over the next decade.

​How to Evaluate P/E Correctly

• ​Compare Within the Same Sector: Never compare an IT company's P/E to a steel manufacturer. Compare Tata Consultancy Services against Infosys, or Tata Motors against Maruti Suzuki.

• Check Historical Bands: Is the company trading above or below its own 5-year and 10-year median P/E?

• Look at the PEG Ratio: Divide the P/E by the company’s expected earnings growth rate. A P/E of 30 for a company growing earnings at 30% (PEG = 1) is often much cheaper than a P/E of 15 for a company growing at 5% (PEG = 3).

​The Takeaway

​P/E is a relative tape measure, not an absolute verdict. A stock is only truly expensive if its future profit growth cannot justify the premium multiple you are paying today.