P/E Ratio Explained: How to Value a Stock the Easy Way
The price to earnings ratio tells you how many rupees you are paying for every one rupee of a company’s yearly profit. P/E ratio is the market price of one share divided by earnings per share, or EPS, for the last four reported quarters. A stock at Rs 600 that earned Rs 30 per share has a P/E of 20, so the market wants Rs 20 for each Rs 1 of current profit.
It is the quickest sanity check in stock analysis and the most abused. A low P/E is not automatically a bargain, and a high P/E is not automatically a bubble.
Below: the arithmetic, trailing versus forward P/E, how to judge whether a number is expensive, a worked example on two stocks priced identically, and the four cases where the ratio misleads.
How is the P/E ratio calculated?
Two inputs, one division. Price is the last traded price on your screen. EPS is net profit after tax divided by outstanding shares, and it sits at the bottom of the profit and loss statement filed every quarter.
So P/E = price per share divided by EPS.
You can also flip it. A P/E of 20 means an earnings yield of 1 divided by 20, which is 5%, and that puts a stock on the same footing as a deposit rate. At a P/E of 50 the earnings yield is 2%.
Where to find EPS without guessing
Use diluted EPS, which assumes stock options and convertibles turn into real shares. Use consolidated figures for any group with subsidiaries. Our walkthrough on how to read an income statement shows where profit and share count sit.
Trailing P/E versus forward P/E
Trailing P/E uses profit that already happened. Factual, backward looking.
Forward P/E uses an estimate of next year’s profit. More relevant, less reliable, because analysts revise those spreadsheets every quarter.
Beginners often stack one company’s trailing P/E against another’s forward P/E and conclude the second is cheaper. That comparison is meaningless. Pick one basis and stay on it.
What counts as a good P/E ratio?
There is no universal number. A cement company, a private bank and a fast growing consumer brand deserve different multiples because their growth rates and profit stability differ.
Judge a P/E against three reference points only: the company’s own history, its closest listed peers, and its earnings growth rate.
| P/E level | What the market is usually saying | What to check next |
|---|---|---|
| Below 10 | Low growth, cyclical peak profit, or a governance concern | Is last year’s profit repeatable? |
| 10 to 20 | Steady, mature business with moderate growth | Debt levels and return on equity |
| 20 to 40 | Above average growth expected for several years | Is growth actually accelerating? |
| Above 40 | Rapid growth priced in, or profit temporarily depressed | What if growth halves? |
| Negative or blank | The company made a loss, so P/E does not exist | Use price to sales or price to book |
Treat those bands as a map, not a rule. Multiples drift with interest rates, so check current sector figures on a screener.
Worked example: two stocks at Rs 600
Company A and Company B both trade at Rs 600 per share.
- Company A: net profit Rs 300 crore, 10 crore shares. EPS = 300 / 10 = Rs 30. P/E = 600 / 30 = 20.
- Company B: net profit Rs 120 crore, 10 crore shares. EPS = 120 / 10 = Rs 12. P/E = 600 / 12 = 50.
On screen, B looks two and a half times dearer. Now add growth: suppose A grows EPS at 8% a year and B at 40%, for three years.
A: 30 x 1.08 = Rs 32.4, then Rs 34.99, then Rs 37.79.
B: 12 x 1.40 = Rs 16.8, then Rs 23.52, then Rs 32.93.
If both prices stayed at Rs 600, A would trade at 600 / 37.79 = 15.9 times year three earnings and B at 600 / 32.93 = 18.2 times. A 30 point P/E gap nearly vanished in three years.
That is what “growth justifies the multiple” means. The trap is the assumption. If B grows at 15% instead, year three EPS is Rs 18.25 and Rs 600 is still 32.9 times earnings. You paid for growth that never came.
A shortcut is PEG: P/E divided by expected growth in percent. B at 40% growth has a PEG of 1.25. At 15% growth it is 3.3, expensive by most standards.
Where the P/E ratio quietly lies
Four cases cause most of the damage.
- One off profits. A company sells land, profit jumps, and the P/E crashes to 6. Next year the gain is gone and the ratio doubles. Strip out exceptional items first.
- Cyclical peaks. Metal and commodity businesses earn their best profits at the top of a cycle, exactly when their P/E looks lowest. The low multiple is the warning, not the invitation.
- Heavy debt. P/E ignores the balance sheet. Two companies with identical EPS can carry very different loan books, and the one with more borrowing is riskier at the same multiple.
- Accounting choices. Depreciation policy and tax treatment shift reported profit without changing the business.
P/E also breaks down for loss making companies and for lenders, where price to book is the better lens. Value and growth names behave differently across a cycle, the theme of our piece on growth stocks versus value stocks.
A five step way to use P/E without fooling yourself
- Take diluted, consolidated, trailing twelve month EPS, and remove any exceptional item.
- Divide price by that adjusted EPS to get your own P/E rather than the site default.
- Compare it with the company’s five year median. A stock at half its own history needs a reason.
- Compare it with two or three genuine peers of similar size. Checking market capitalisation stops you stacking a small cap against an index heavyweight.
- Divide the P/E by expected growth. If the answer is far above 2, ask what must go right.
Risk note: valuation ratios describe expectations, not outcomes. A cheap P/E can stay cheap for years, and a stock can fall even while earnings rise.
Frequently Asked Questions
Can a P/E ratio be negative?
Not meaningfully. A loss makes EPS negative, and the arithmetic then produces a number carrying no information about value, which is why most screeners simply leave the field blank. For loss making companies use price to sales or price to book instead.
Why do two websites show different P/E ratios for the same stock?
Because they use different EPS inputs. One may use standalone profit, another consolidated. One may use the last four quarters, another the last full financial year. Some adjust for exceptional items and some do not, so check the basis before comparing across platforms.
Is a P/E of 15 always better than a P/E of 45?
No. The 15 could be a cyclical business at peak profit heading into a downturn, and the 45 could be a company compounding earnings at 35% a year. Multiples make sense only next to growth, debt and profit quality, so compare within a sector and against the company’s own history.
How is P/E different from the index P/E of Nifty?
The index P/E aggregates the earnings of all constituents against their combined market value, weighted by free float. It is a market temperature reading rather than a stock signal, and exchanges publish it daily. Traders use it to sense whether the broad market sits above its own long run range.
Does the P/E ratio change after a stock split or bonus issue?
No, and that is the point. A split or bonus raises the share count and cuts price and EPS in the same proportion, so the ratio holds. If a P/E appears to jump right after such a corporate action, the data provider has probably not yet adjusted historical EPS for the new share count.
Should I use P/E or charts to time my entry?
They answer different questions. P/E helps decide what is worth owning; price action helps decide when to act. Many investors shortlist on fundamentals, then pick levels from charts, a split covered in our comparison of technical and fundamental analysis.
Key Takeaways
- P/E equals price divided by EPS, so a P/E of 20 means Rs 20 per Rs 1 of annual profit and an earnings yield of 5%.
- Compare trailing with trailing, or forward with forward. Mixing the two is the most common beginner error.
- Use diluted consolidated EPS with exceptional items removed, or a land sale will make an ordinary company look cheap.
- A high multiple is justified only by growth that shows up: 40% EPS growth closed a 30 point gap in three years, while 15% growth did not.
- Divide P/E by expected growth for a PEG check. Readings far above 2 need a specific reason.
- P/E is blind to debt and useless for loss makers and most lenders, so pair it with price to book.
