PE Ratio Meaning, Formula & How to Know if a Stock is Expensive

The PE ratio, or Price-to-Earnings ratio, tells you how much investors are paying for every ₹1 of a company’s earnings.

For example, if a stock has a PE ratio of 20, it means investors are paying ₹20 for every ₹1 the company earns.

But PE is not a magic number. A high PE does not always mean a stock is expensive. A low PE does not always mean a stock is cheap. You need to compare PE with earnings growth, sector average, company quality, and business risk.

What is the PE Ratio? Meaning

PE ratio stands for Price-to-Earnings ratio. It compares a company’s share price with its earnings per share, or EPS.

In simple words:

PE ratio shows how much the market is willing to pay for a company’s profit.

Think of it like buying a business. If a company earns ₹10 per share and the share price is ₹200, the market is valuing that stock at 20 times its earnings.

So the PE ratio is 20.

This means investors are paying ₹20 for every ₹1 of earnings.

PE is useful because share price alone can be misleading. A ₹100 stock is not automatically cheaper than a ₹1,000 stock. What matters is how much profit each share earns compared with its price.

That is why PE connects two important things:

Before using PE ratio, you should understand EPS first. EPS means profit per share. If needed, read EPS: Earnings Per Share before this chapter.

PE Ratio Formula and How to Calculate It

The PE ratio formula is:

PE Ratio = Current Market Price Per Share ÷ Earnings Per Share

Let’s take a simple example.

A stock is trading at ₹500.

Its EPS is ₹25.

So:

₹500 ÷ ₹25 = 20 PE

This means the stock is trading at 20 times its earnings.

In simple words, investors are paying ₹20 for every ₹1 the company earns.

Now take another example.

Both stocks trade at ₹500. But Company B is more expensive based on earnings because its PE is 50.

This is why PE is better than looking at share price alone.

A beginner mistake is thinking that a ₹100 stock is cheap and a ₹2,000 stock is expensive. That is not how valuation works.

A ₹2,000 stock with strong earnings may be cheaper than a ₹100 stock with weak earnings.

The real question is:

How much profit are you getting for the price you are paying?

What is a Good PE Ratio for Indian Stocks?

There is no single good PE ratio for all Indian stocks.

A PE of 15 may be high for one company and low for another. It depends on the company’s sector, growth rate, profit stability, debt level, and business quality.

For learning purposes, you can think of it like this:

The important word is may.

Low PE does not always mean undervalued.

High PE does not always mean overvalued.

Example: a company with a PE of 50 may still be attractive if its earnings are growing very fast and the business has strong quality. But a company with a PE of 8 may be risky if profits are falling, debt is high, or the sector is in trouble.

For beginners, the safer rule is:

Do not ask “Is this PE high or low?” Ask “Is this PE justified by the company’s growth and quality?”

PE Ratio by Sector in India: Where It Works Better

PE ratios vary widely across sectors.

This happens because different sectors have different growth rates, profit stability, capital needs, and business risks.

For example, FMCG companies often trade at higher PE ratios because their products are used daily and profits are usually stable. Capital goods companies may also trade at higher PE during strong investment cycles because investors expect future earnings growth.

Here are broad learning benchmarks for Indian sectors:

Use these only as broad learning ranges. They are not fixed rules.

An FMCG stock at 45 PE may still be reasonable if earnings are consistent and the brand is very strong. An auto stock at 18 PE may still be risky if demand is slowing or margins are under pressure.

The practical rule is:

Compare a company’s PE with its own sector, not with a completely different sector.

Do not compare an FMCG company with an auto company. Their business models, margins, growth rates, and risks are different.

A better comparison is:

PE makes more sense when the companies have similar business models.

For banks, NBFCs, and financial services companies, PE is not usually the best starting ratio. These businesses need separate metrics like PB ratio, ROE, asset quality, NIM, credit cost, and capital adequacy. We will cover this separately in the PB Ratio chapter.

Trailing PE vs Forward PE: Which to Use?

There are two common types of PE ratios: trailing PE and forward PE.

Trailing PE usually uses earnings from the last 12 months. This is also called TTM PE, where TTM means trailing twelve months.

Forward PE uses expected earnings for the next year or future period.

Example:

A stock trades at ₹1,000.

Its last 12-month EPS is ₹50.

Trailing PE is:

₹1,000 ÷ ₹50 = 20

Now suppose analysts expect next year’s EPS to be ₹80.

Forward PE becomes:

₹1,000 ÷ ₹80 = 12.5

The same stock looks cheaper on forward PE because earnings are expected to grow.

But remember one thing:

Trailing PE is based on actual numbers. Forward PE is based on estimates.

Forward PE can be useful, but it can also be wrong. Earnings estimates may change if demand slows, margins fall, costs rise, or management guidance changes.

For beginners, the best approach is:

Use trailing PE for reality. Use forward PE for expectations. Do not rely only on forward PE.

How to Use PE Ratio for Stock Analysis

PE ratio becomes useful when you compare it properly.

Do not look at PE in isolation. Use it as one part of your stock analysis.

Here is a simple workflow.

Let’s make this practical. Suppose an IT company trades at 28 PE.

That number alone does not tell you much.

You should ask:

This is how experienced investors use PE. They do not treat it like a buy or sell signal.

They use it as a starting point for deeper analysis.

The cleanest way to remember it:

PE tells you the market’s expectation. Your job is to check whether the business can justify that expectation.

PEG Ratio: PE Adjusted for Growth

The PEG ratio improves the PE ratio by adding growth into the picture.

The formula is:

PEG Ratio = PE Ratio ÷ EPS Growth Rate

EPS growth rate means how fast the company’s earnings per share are growing.

Example:

A company has a PE ratio of 30.

Its EPS is growing at 30% per year.

So:

30 ÷ 30 = 1 PEG

Now take another company.

It also has a PE ratio of 30.

But its EPS is growing at only 10% per year.

So:

30 ÷ 10 = 3 PEG

Both companies have the same PE. But the first company looks more reasonable because its earnings are growing faster.

For beginners, this is the simple interpretation:

Do not use PEG blindly.

A low PEG does not guarantee a good stock. Growth may slow down. Earnings may be cyclical. One-year growth may be unusually high.

Use PEG as a second check after PE, especially for growth stocks.

The practical rule is:

PE tells you the price of earnings. PEG tells you whether the growth may justify that price.

Limitations of PE Ratio

PE ratio is useful, but it has serious limitations.

The biggest limitation is this:

PE only works when a company has positive earnings.

If a company is loss-making, EPS is negative. In that case, PE becomes meaningless. This is why many broker apps show PE as N/A or blank for loss-making companies.

Here are the main limitations:

Here is a common trap.

A stock falls sharply. Its PE becomes low. A beginner thinks, “This is cheap now.”

But sometimes the market is not being irrational. It may be expecting earnings to fall.

If EPS falls later, the stock may not actually be cheap.

Example:

A stock trades at ₹500 and EPS is ₹50.

PE is:

₹500 ÷ ₹50 = 10

Now suppose earnings fall and EPS becomes ₹20.

At the same ₹500 price, PE becomes:

₹500 ÷ ₹20 = 25

The stock that looked cheap at 10 PE can suddenly look expensive if earnings collapse.

This is called a value trap.

A value trap is a stock that looks cheap based on numbers but keeps falling because the business is getting weaker.

For highly leveraged companies, also look beyond PE. Debt-heavy companies may need ratios like EV/EBITDA because PE does not fully capture debt risk.

For beginners, the rule is:

Low PE is not enough. Check why the PE is low.

PE Ratio vs PB Ratio: When to Use Which

PE ratio and PB ratio both help you judge valuation, but they are used in different situations.

PE ratio compares price with earnings.

PB ratio compares price with book value.

Book value roughly means the company’s net assets after subtracting liabilities from assets.

Here is the simple difference:

PE is useful when earnings are meaningful and stable.

PB is more useful when the balance sheet matters more than short-term earnings. This is why PB ratio is commonly used for banks, NBFCs, and financial services companies.

But PB ratio also has limitations. A low PB bank is not automatically cheap if asset quality is poor, loan growth is weak, or credit costs are rising.

For beginners, use this simple rule:

For a deeper explanation, read PB Ratio: Meaning, Formula & How to Use It.

Final Takeaway

PE ratio shows how much investors are paying for every ₹1 of a company’s earnings.

The formula is simple:

PE Ratio = Current Market Price Per Share ÷ Earnings Per Share

But using PE well requires context.

The most important lesson is this:

PE ratio is not a final answer. It is a starting question.

A high PE stock can still be worth studying if earnings growth is strong. A low PE stock can still be risky if profits are falling.

Use PE with sector comparison, earnings growth, cash flow, debt, and business quality. That is how the ratio becomes useful for real stock analysis.