What Is PE Ratio? Definition, Formula & Smart Ways to Use It in Investing

Exploring Key Types of PE Ratios Investors Should Know

Understanding the various types of PE ratios and their applications would allow an investor to assess a stock more accurately by putting its valuation into the right perspective.

• Trailing PE Ratio
  • This ratio is based on the actual earnings earned in the past 12 months.
  • Shows how the stock has performed historically.
  • Commonly used in financial reports.
• Forward PE Ratio
  • Uses forecasted earnings over the next 12 months.
  • Reflects market expectations for future growth.
  • Ideal for evaluating fast-growing firms.
• Normalised PE Ratio
  • Adjusts for temporary gains or losses.
  • Smoother and more accurate for cyclical companies.
• Shiller PE Ratio (CAPE – Cyclically Adjusted PE)
  • Based on inflation-adjusted earnings over 10 years.
  • Often used for broader market valuation.

Different PE ratios give different insights. Trailing PE analyses past earnings to show how a stock has done historically, while forward PE uses future estimates to predict growth of the stock. Understanding different types of PE ratios can help investors make smarter decisions to find the best PE ratio stocks to invest in
 

Fundamentals of PE Ratio

P/E ratio is the price of a company's share divided by its earnings per share. The earnings, as the company reports them, are gross earnings.

Gross earnings is the value left over after all expenses, including taxes and interest on debt, have been paid. So-net profits are higher than gross profits. And net profits are higher than reported earnings.

But what is "net?" It is a lot less than gross. In some countries, like Japan, it can be a lot less. In most countries, the difference is not so extreme, but it is still there. So P/E ratios tend to be higher than they would be if we were using net earnings instead of reported earnings.

P/E ratio stands for the price to earnings ratio. Many people in the stock market use P/E because it shows how much you are paying for a dollar of profit.

How is P/E Ratio calculated?

The P/E ratio is calculated by dividing the market price of a share by its earnings per share. The result is then multiplied by 100. A PE ratio of 8, for example, means that for every rupee of profit earned by the company, the shares are being sold at 8 rupees. A PE ratio of 15 means it's being sold at 15 rupees for every rupee of profit.

E.g., if the P/E Ratio of TCS is ten, it means that the current market price of TCS is ten times its EPS.

P/E Ratio Formula = Price Per Share / Earnings Per Share

The PE ratio of a company tells us at what price investors are buying or selling the company's shares. The higher the PE ratio of a company, the more expensive it is for investors to buy shares, so you can say that if the PE ratio of a company increases, then the value of its shares will also increase.

On the other hand, if the PE ratio of a company decreases, then its share value will also decrease because investors are finding it cheaper to purchase more shares, given that they are paying less money for each share.

How to Calculate PE Ratio: Simple Formula

The formula for the Price to Earnings Ratio is given below,

PE Ratio = Market Price (Per Share) / Earnings Per Share (EPS)

Example:

If a company’s stock is ₹150 and EPS is ₹15,

PE Ratio = 150 / 15 = 10

This means that investors are willing to spend ₹10 for each ₹1 the company generates in earnings. A low PE ratio might point to a potentially undervalued stock, whereas a high PE ratio often reflects strong growth expectations, or, in some cases, an overpriced stock.

This formula helps in comparing stocks and choosing the best PE ratio stocks for your portfolio. Knowing the PE full form in the share market is one thing; using it through this formula is what drives smart decision-making.
 

Absolute vs. Relative PE: Which Offers Better Valuation Insight?

Two common approaches in valuation are absolute PE and relative PE. Here’s how they differ,

• Absolute PE
  • Evaluates a stock's PE in isolation.
  • It answers: Is this stock cheap or expensive based on its own earnings?
• Relative PE
  • Compares a stock’s PE to industry peers, historical averages, or market benchmarks.
  • This measure helps determine if it's undervalued or overvalued relative to similar companies.

For example, a stock with an absolute PE of 20 may seem fair, but if peers average 15, it might be overpriced. Relative PE adds context and improves clarity in valuation decisions.

Using both approaches can help investors better interpret the PE ratio's meaning and explore undervalued or overhyped stocks in the financial market.
 

Absolute vs. Relative PE: Which Offers Better Valuation Insight?

Two common approaches in valuation are absolute PE and relative PE. Here’s how they differ,

Absolute PE

• Evaluates a stock's PE in isolation.
• It answers: Is this stock cheap or expensive based on its own earnings?

Relative PE

• Compares a stock’s PE to industry peers, historical averages, or market benchmarks.
• This measure helps determine if it's undervalued or overvalued relative to similar companies.

For example, a stock with an absolute PE of 20 may seem fair, but if peers average 15, it might be overpriced. Relative PE adds context and improves clarity in valuation decisions.

Using both approaches can help investors better interpret the PE ratio's meaning and explore undervalued or overhyped stocks in the financial market.
 

How to determine the P/E Ratio?

There are two ways to find out what the PE ratio is. You can look it up in a reference book, or you can do the math yourself.

The second method may not sound as convenient as the first, but it's easier than you might expect. It just requires that you know how to use three elementary formulas:

• one for calculating earnings per share (EPS),
• one for calculating the market price per share (market price divided by the total number of shares outstanding), and
• one for calculating PE ratio (market price divided by EPS).

The last formula is simply the reciprocal of the other two: 1 divided by market price divided by EPS.

P/E ratio = Price/Earnings

P/E ratio is a measure of a stock's market value relative to the net profit it generates.

If a company has a high P/E ratio, investors are willing to pay a significant price for each rupee of profit the company makes. For example, if XYZ stock has a P/E ratio of 100, it means that investors are willing to pay ₹100 for every ₹1 of profit made by XYZ.

If a company has a low P/E ratio, investors are not paying much for each rupee of profit made by the company. For example, if the P/E ratio of a company is 10, it means that investors are only willing to pay ₹10 for every ₹1 of profit made by the company.

How to use P/E Ratios for Stock Market Investing?

The price-to-earnings ratio, or pe ratio, is the most common way to value a stock. It's also one of the concepts in finance that's hardest to understand.

There are pe ratios for individual companies and the market as a whole. The pe ratio for a company is usually written as price/earnings or p/e. For the market as a whole, it's written as price/earnings-to-growth, or p/eg (though you'll also see it written pe/e.g.).

It works by taking the company's stock price and dividing by its earnings per share (EPS), then multiplying by some growth rate. The result tells you how much you need to grow your earnings every year to justify the current stock price. If you don't think the company will grow that fast, you should wait until it does before buying its stock.

The best time to determine whether to buy or sell is when the stock gets close to its 52-week high.

The price/earnings ratio is an economic measure of the relationship between the price of a share of stock and the earnings per share. It is calculated by dividing the current market price of a share by its earnings per share.

What is a Good P/E Ratio?

There is no one-size-fits-all “good” P/E ratio, what’s considered favourable depends heavily on the sector, the company’s growth prospects, and market conditions.

Some broad guiding principles:

Relative Comparison Matters

A good P/E ratio is often one that is reasonable compared to peers in the same industry.

• For example, a utility company (which tends to be stable but slow-growing) might have a P/E in the lower end.
• In contrast, a high-growth technology business might command a significantly higher P/E because investors expect earnings to grow fast.

Growth Expectations

Companies with strong future earnings growth potential can justify a higher P/E. If earnings are expected to rise sharply, investors may be willing to pay a premium.

However, if growth is uncertain or earnings are volatile, a lower P/E might be more appropriate.

Historical and Market Context

Looking at a company’s historical P/E and comparing it to broad market averages can help.

Also, the average P/E for a broad index (or a benchmark) can give reference points. For instance, historically many broad indices have had average P/Es in a moderate range (though this varies widely).

Use with Other Metrics

Because P/E does not consider all factors (like debt, cash flow, extraordinary items), it should be used in combination with other valuation metrics, such as PEG ratio (which adjusts P/E for growth), cash-flow-based ratios, or return ratios.

Risk Considerations

A very high P/E can sometimes signal overvaluation (or very optimistic growth expectations), while a very low P/E might indicate undervaluation or possibly risk (if earnings are weak or declining).

Also, accounting practices, one-off earnings, or even creative accounting can distort earnings, making P/E misleading in isolation.

Smart Ways to Use PE Ratio in Stock Analysis

The PE ratio is more insightful when combined with broader analysis. Here are some proven best practices,

• Do:
  • Compare PE ratios within the same sector.
  • Use both trailing and forward PE for a full picture.
  • Combine with other metrics like PEG ratio, ROE, or debt levels.
• Don’t:
  • Compare across unrelated industries.
  • Make decisions on PE alone, context is crucial.
  • Ignore fundamentals or one-time events that distort earnings.

By following these smart practices, investors can clearly understand the PE full form in the share market and avoid common errors in stock valuation. This approach plays a crucial role in spotting the best PE ratio stocks that align with your investment objectives and risk appetite.
 

Why Do Investors Look at P/E Ratios?

Investors look at PE Ratio while taking an investment decision. They invest in companies where earnings are growing faster than the stock price. In such a case, they believe that its earnings will ultimately justify its high price tag.

PE Ratio can be used to compare one company against another or even across sectors. Also, it helps in determining whether a company is undervalued or overvalued relative to its peers or underlying fundamentals.

It is easy to calculate how much money a company makes on each rupee invested by the shareholders through its Profit per Share (PPS) and further divide it by the current share price to develop a PE ratio for that company.

P/E Ratio vs Earnings Yield

The earnings yield is the reverse of the P/E ratio. It shows how much a company earns for every rupee you invest, calculated as EPS divided by stock price, expressed in percentage terms.

For example, if a stock trades at ₹100 and its EPS is ₹5, the P/E is 20 and the earnings yield is 5%. Another stock at ₹200 with ₹20 EPS has a P/E of 10 and a 10% earnings yield.

Though not as popular as the P/E ratio, earnings yield helps investors compare potential returns, especially when evaluating low-profit or loss-making companies. While a negative P/E is shown as “N/A,” a negative earnings yield still gives a comparison point, particularly for startups or high-growth firms.
 

P/E Ratio vs PEG Ratio

The PEG ratio combines the P/E ratio with earnings growth to offer a fuller picture of a stock’s value. It’s calculated by dividing the P/E ratio by the expected earnings growth rate.

If a company has a P/E of 20 and is expected to grow earnings at 20% annually, the PEG is 1. A PEG below 1 may signal undervaluation, while a PEG above 1 might suggest the stock is overpriced relative to its growth.

PEG is more insightful than P/E alone, especially in sectors like tech or pharma where growth is rapid. Investors can use either past growth (trailing PEG) or future projections (forward PEG) to assess if the price justifies the growth outlook.
 

Wrapping Up

PE Ratio is an important financial term. It denotes the relative "cheapness" or "expensiveness" of a company compared to its competitors. Diving into the numbers of a company represents some risk for making mistakes in a company's actual earnings. Understanding PE Ratio will facilitate your investment decisions.