Quick explanation: The price-to-earnings (P/E) ratio compares a company's share price with its earnings per share (EPS). It shows how much investors are paying for each ₹1 of the company's annual earnings. P/E helps compare valuations, but on its own it does not prove that a stock is cheap or expensive.
The P/E formulas
For a company with positive earnings:
An equivalent company-level formula is:
The market cap and the earnings must refer to the same ownership basis, and EPS and profit must cover the same earnings period. For a simple teaching example, assume a constant share count and no special adjustments.
Understanding earnings per share (EPS)
EPS expresses the earnings attributable to ordinary shareholders on a per-share basis. In a simplified example:
In actual financial reporting, basic EPS generally uses the weighted-average number of ordinary shares during the reporting period, with relevant adjustments. That is why published EPS may not equal annual profit divided by the latest share count exactly. The S05 article in this series covers revenue, profit and EPS in more detail.
Worked example: P/E from share price and EPS
Assume Company A has:
| Particular | Value |
|---|---|
| Share price | ₹200 |
| Annual EPS | ₹10 |
= 20×
Interpretation: investors are valuing the company's equity at ₹20 for every ₹1 of annual earnings per share. This is a valuation multiple. It is not a promised return, and it does not mean the investment will pay for itself in exactly 20 years.
The flip side: earnings yield. Dividing earnings by price gives the earnings yield. At a P/E of 20×, earnings yield is 1 ÷ 20 = 5%. Some investors compare earnings yield with bond yields as a rough sense check, keeping in mind that earnings are not paid out in full and can change.
Worked example: P/E from market cap and annual profit
Assume Company B has:
| Particular | Value |
|---|---|
| Share price | ₹500 |
| Outstanding shares | 10 crore |
| Full market cap | ₹5,000 crore |
| Annual profit attributable to equity shareholders | ₹250 crore |
Step 1 — Full market cap
Step 2 — Simplified EPS
Step 3 — P/E calculated two ways
P/E = ₹5,000 crore ÷ ₹250 crore = 20×
Both methods give the same result when share counts and earnings bases are aligned.
How to interpret a high or low P/E
Consider two hypothetical companies:
| Particular | Company X | Company Y |
|---|---|---|
| Share price | ₹300 | ₹300 |
| Annual EPS | ₹10 | ₹20 |
| P/E | 30× | 15× |
Company X trades at a higher earnings multiple. That may reflect expectations of faster future growth, better business quality, or optimism — or simply an expensive valuation. Company Y's lower multiple may indicate better value, slower expected growth, higher risk, or temporarily inflated earnings.
A P/E ratio must be judged alongside growth, business quality, risk and the earnings period. Comparing a bank's P/E with a consumer company's, or a cyclical metal producer's at the peak of a commodity cycle with a software company's, can mislead badly.
Real multiples vary widely. In the indicative October 2026 snapshot on our Nifty 50 sector dashboard, the reported P/Es of the 50 companies ranged from below 7× to above 700×, which shows how much sector, growth expectations and the earnings base can matter.
What happens when price or earnings change
Start with a share price of ₹200 and annual EPS of ₹10: a P/E of 20×.
| Scenario | Share price | Annual EPS | P/E |
|---|---|---|---|
| Starting position | ₹200 | ₹10 | 20× |
| Price rises 50%; EPS unchanged | ₹300 | ₹10 | 30× |
| EPS rises 50%; price unchanged | ₹200 | ₹15 | 13.33× |
Earnings-rise P/E = ₹200 ÷ ₹15 ≈ 13.33×
The P/E ratio moves whenever either input moves. This introduces P/E expansion and contraction, covered in depth in S06.
Can P/E be used for Nifty 50?
Yes. A P/E can be calculated for a group of companies using aggregate, consistently measured equity market value and attributable earnings. For example, in a simplified full-market-cap-based illustration:
| Particular | Hypothetical Nifty 50 aggregate |
|---|---|
| Combined full market cap | ₹200 lakh crore |
| Combined annual attributable earnings | ₹10 lakh crore |
Important: this is not the published NSE Nifty 50 P/E. Nifty 50 uses a free-float-adjusted index methodology. Do not divide free-float-adjusted market cap by unadjusted total earnings and call the result the official index P/E. The S10 article in this series shows how sector-level aggregate P/E is calculated correctly.
Important limitations of P/E
- Zero or negative earnings make a conventional positive P/E meaningless; such cases are usually shown as "not meaningful".
- Trailing twelve months (TTM), financial-year (FY) and forward earnings produce different P/E figures; see S07.
- One-off gains or losses, cyclical profits and accounting differences can distort comparisons.
- Standalone and consolidated profits can give very different P/Es for the same company; see S09.
- Financial and non-financial companies often need different analytical context.
- A low P/E does not automatically mean undervaluation, and a high P/E does not automatically mean overvaluation.
Growth-adjusted views. Some investors divide P/E by the expected earnings growth rate to get the PEG ratio, as a rough way to compare companies growing at different speeds. It inherits all the uncertainty of the growth estimate.
Key takeaways
- P/E measures how much the market pays for each ₹1 of annual earnings.
- P/E = Share Price ÷ EPS, or Full Market Cap ÷ aligned attributable earnings.
- A 20× P/E means ₹20 of equity market value per ₹1 of annual earnings, not a 20-year payback promise.
- Rising prices with unchanged earnings increase P/E; rising earnings with unchanged prices reduce it.
- Always compare P/E on a consistent earnings period and ownership basis.
All company figures in the worked examples are hypothetical teaching inputs.
An account with P/E and EPS on every stock
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Frequently Asked Questions
What is the P/E ratio?
The share price divided by earnings per share. It shows how many rupees investors are paying for each rupee of a company's annual earnings.
How do you calculate P/E using market cap?
Divide full equity market cap by net profit attributable to equity shareholders, making sure both use the same ownership basis and earnings period.
Is a low P/E stock always cheap?
No. A low P/E can reflect slow growth, high risk or temporarily high earnings. P/E must be judged with growth, quality and the earnings period.
What does a P/E of 20 mean?
That the market values the equity at ₹20 for every ₹1 of annual earnings. It is a valuation multiple, not a promise of returns or a payback period.
What is the official Nifty 50 P/E?
It is published by NSE Indices using its own methodology. A simple full-market-cap calculation is an illustration, not the official figure.
Related Reading
- When the multiple itself changes
- Which earnings period the P/E uses
- From revenue down to EPS
- Other ratios used in stock analysis
- Low-multiple versus high-growth styles
- Sector-level P/E done properly
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