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§01 · INSIGHTS · LEARN · 12 MIN · DEEP DIVE

P/E Ratio (Price-to-Earnings): Definition, Calculation, and Interpretation

The Price-to-Earnings ratio divides a stock's current share price by its earnings per share. Learn how trailing vs. forward P/E differ, what Nifty 50's historical ~20× average means, and why sector context is essential.

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Contents
  1. Definition
  2. How It Is Computed
  3. What High/Low Values Signal
  4. Sector Dependency
  5. Worked Example
  6. Caveats
  7. See Also
  8. Primary Source

Definition

The Price-to-Earnings (P/E) ratio is the most widely quoted valuation multiple in equity markets. It expresses how many rupees an investor pays for every one rupee of annual earnings the company generates:

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

Two variants dominate practice. Trailing P/E (TTM — Trailing Twelve Months) uses actual reported EPS from the four most recent quarters, anchored in audited numbers. Forward P/E uses analyst consensus EPS estimates for the next twelve months. A third variant, the cyclically-adjusted P/E (CAPE or Shiller P/E), averages inflation-adjusted earnings over ten years to smooth business-cycle distortions — widely used in academic literature (Campbell & Shiller 1988).

How It Is Computed

Data inputs:

  • Numerator: last traded price (LTP) from NSE/BSE at a given close.
  • Denominator (TTM): sum of diluted EPS from the four most recent quarterly results filed under SEBI LODR 2015 Regulation 33. Data aggregators (NSE website, BSE Corporate Filing, Screener.in) compile these automatically.
  • Denominator (Forward): median of sell-side EPS estimates for FY+1 from Bloomberg, Refinitiv, or domestic platforms.

Adjustments: (a) exclude extraordinary one-off items (asset sale gains, insurance settlements) to get normalised EPS; (b) strip deferred-tax reversals; (c) P/E is undefined for loss-making companies (shown as N/M). Nifty 50 index-level P/E is published daily by NSE at nseindia.com as aggregate market cap ÷ aggregate TTM earnings.

What High/Low Values Signal

The academic literature treats P/E as a predictor of long-run returns. Fama & French (1992) documented that low P/E (value) stocks earned higher average returns than high P/E (growth) stocks in US data 1963–1990; Sehgal & Balakrishnan (2002, Vision journal) found similar value premia in BSE data. Debate exists on whether this is risk compensation or investor overreaction (Lakonishok, Shleifer & Vishny 1994).

Nifty 50 TTM P/E has ranged from approximately 10× (March 2020 COVID trough) to 40× (October 2021 peak), with a long-run median near 20× per NSE historical data. The historical academic literature classifies stocks with P/E below the category-median as “value” and above as “growth” (Fama-French 1992) — a descriptive classification, not a buy/sell threshold.

Sector Dependency

P/E norms vary sharply. FMCG and consumer-tech companies routinely trade above 40–50×. Infrastructure, utilities, and PSU banks historically trade at 8–14×. Auto OEMs average 12–18× through a cycle. Pharma and IT services occupy 20–30×. Comparing a PSU bank’s P/E with an FMCG company is therefore misleading. NSE publishes sub-index P/E (Nifty Bank, Nifty IT, Nifty FMCG) as more meaningful sector benchmarks.

Worked Example

Infosys Ltd (NSE: INFY) — data as of BSE filing, April 2025

Infosys FY2025 annual diluted EPS (consolidated, INR): approximately ₹66.73 per Infosys investor relations. At approximately ₹1,580 (NSE closing, April 2025):

TTM P/E = ₹1,580 ÷ ₹66.73 ≈ 23.7×

Five-year trailing P/E range: 16× (FY2020 COVID low) to 38× (FY2022 peak). Nifty IT index P/E was approximately 26× at the same date, placing Infosys slightly below sector median. Forward P/E on FY2026 consensus EPS of ~₹72 gives approximately 21.9×. Figures are approximate; verify with current NSE/BSE data.

Caveats

  • Debt blindness: Two companies with identical P/E can have vastly different leverage. EV/EBITDA or P/FCF are more debt-neutral comparisons.
  • Accounting choices: Depreciation method, revenue recognition timing, and inventory valuation (Ind AS 2) all affect reported EPS and hence P/E.
  • Cyclicality: For cyclical sectors, P/E at cycle peaks is deceptively low, at troughs deceptively high. CAPE addresses this but requires long data series.
  • Negative earnings: P/E is undefined for loss-making companies; EV multiples or price-to-sales are used instead.

See Also

Primary Source

  • NSE India Historical Index Data (Nifty 50 P/E series): nseindia.com
  • Fama, E. & French, K. (1992). “The Cross-Section of Expected Stock Returns.” Journal of Finance, 47(2), 427–465.
  • SEBI LODR 2015, Regulation 33: sebi.gov.in

Disclosure: MintByte is registered with AMFI as a Mutual Fund Distributor (ARN-314872) and with APMI as a Portfolio Management Services distributor (APMI APRN-01658). The content on this page is educational and informational only. Nothing here constitutes investment advice, a recommendation to buy or sell any security, or a solicitation of any offer. Equity investments are subject to market risk. Please read all scheme-related documents and consult a SEBI-registered investment adviser before making any investment decision.

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