The One Number Every Investor Must Understand

If you could only check one metric before buying a stock, it should be the Price-to-Earnings (P/E) ratio. It's the simplest and most widely used tool to figure out whether a stock is cheap, expensive, or fairly valued.

Warren Buffett uses it. Rakesh Jhunjhunwala used it. SEBI-registered analysts use it. And after reading this article, you'll use it too.

What is the P/E Ratio?

The P/E ratio tells you how much investors are willing to pay for every ₹1 of a company's earnings.

Formula:

P/E Ratio = Current Market Price per Share ÷ Earnings per Share (EPS)

Example: If Infosys stock trades at ₹1,500 and its EPS (earnings per share) is ₹60, then:

P/E = 1,500 ÷ 60 = 25

This means investors are paying ₹25 for every ₹1 of Infosys's annual profit. Another way to think about it: at current earnings, it would take 25 years for the company's profits to equal your investment (assuming no growth).

Types of P/E Ratio

Trailing P/E (TTM)

Uses the company's earnings from the last 12 months (Trailing Twelve Months). This is based on actual, reported numbers — no guesswork.

Most financial websites (Moneycontrol, Screener.in, Tickertape) show trailing P/E by default.

Forward P/E

Uses estimated future earnings (analyst projections). It's forward-looking but relies on predictions that can be wrong.

If a company has trailing P/E of 30 but forward P/E of 20, analysts expect earnings to grow 50% next year — which would make the stock cheaper than it looks today.

What is a "Good" P/E Ratio for Indian Stocks?

There's no universal answer, but here are practical benchmarks for the Indian market:

  • NIFTY 50 Average P/E: Historically ranges between 18-24. Above 25 is considered expensive, below 18 is considered cheap.
  • Large-cap stocks: Typically P/E of 15-30. Quality companies (HDFC Bank, TCS, Asian Paints) command premium P/E ratios of 25-50+.
  • Mid/Small-cap stocks: Wide range — anywhere from 8 to 80. High P/E could mean growth potential or overvaluation.
  • PSU/Value stocks: Often P/E of 5-15. Cheap valuations, but growth may be slower.

P/E Comparison — The Right Way

The biggest mistake beginners make is comparing P/E ratios across different sectors. A tech company's P/E of 35 is NOT comparable to a steel company's P/E of 8. Here's how to compare correctly:

  • Compare within the same sector: Infosys (P/E 25) vs TCS (P/E 28) vs Wipro (P/E 22) — now you have a meaningful comparison.
  • Compare with own historical P/E: If HDFC Bank's average P/E over 10 years is 22 and it's currently at 17, it might be undervalued relative to its own history.
  • Compare with sector average: If the IT sector average P/E is 25 and a company has P/E of 15, it's cheaper than peers — but find out why before buying.

Why Do Some Stocks Have Very High P/E?

A stock with P/E of 60 or 100 isn't necessarily overpriced. High P/E usually means one of these:

  • High growth expectations: Investors expect earnings to grow rapidly. Companies like Avenue Supermarts (DMart) or Trent have commanded P/E ratios above 100 because of their consistent growth.
  • Market hype: Sometimes stocks are genuinely overpriced due to speculation (common in IPO-era stocks).
  • One-time earnings drop: If earnings temporarily fell (due to pandemic, one-time expense), P/E shoots up artificially.

Why Do Some Stocks Have Very Low P/E?

A stock with P/E of 5 isn't necessarily a bargain. Low P/E can mean:

  • Cyclical industry: Metal, sugar, and commodity stocks often have low P/E at peak earnings (counter-intuitive but important — low P/E in cyclicals can mean the peak is near).
  • Declining business: The market expects earnings to shrink in the future.
  • Governance concerns: Investors distrust the management or promoters.
  • Genuinely undervalued: The market has overlooked a solid company — this is where value investors find opportunities.

P/E Ratio Limitations — Don't Use It Alone

P/E is powerful but not perfect:

  • Doesn't work for loss-making companies: If EPS is negative, P/E is meaningless. Many new-age companies (Zomato, Paytm at listing) had no P/E because they weren't profitable.
  • Earnings can be manipulated: Companies can inflate EPS through accounting tricks. Always cross-check with cash flow.
  • Ignores debt: A company with P/E of 10 but ₹50,000 crore debt is NOT cheap. Use EV/EBITDA alongside P/E for debt-heavy companies.
  • Backward-looking: Trailing P/E tells you about the past. The stock market prices in the future.

How to Check P/E Ratio — Free Tools

  • Screener.in — Best free fundamental analysis tool for Indian stocks. Shows P/E, historical P/E, and peer comparison.
  • Moneycontrol — Stock quote page shows trailing P/E.
  • Tickertape — Excellent for comparing P/E across peers.
  • Zerodha Kite — Shows P/E on the stock's overview page.

Key Takeaways

  • P/E Ratio = Price ÷ Earnings per Share — it tells you how much you're paying for each rupee of profit
  • Always compare P/E within the same sector or with a stock's own historical average
  • High P/E can mean growth potential or overvaluation — dig deeper to find which
  • Low P/E can be a value opportunity or a warning sign — especially in cyclical industries
  • Never use P/E alone. Combine it with debt levels, cash flow, and growth trajectory for a complete picture
This article is for educational purposes only and does not constitute investment advice. Please consult a SEBI-registered financial advisor before making investment decisions.