Financial Ratios Explained: P/E, ROE, Debt and Profit Margins
When analysing a company, understanding its financial health is an important part of fundamental analysis. This is where financial ratios can help.
Financial ratios allow investors to compare companies and examine areas such as valuation, profitability, efficiency and financial strength.
This guide looks at four widely used financial ratios, P/E, Return on Equity, Debt-to-Equity and profit margin, and what each can tell us about a business.
What Are Financial Ratios?
Financial ratios work similarly to a medical health check-up. A doctor may look at blood pressure, heart rate and cholesterol levels to build a complete picture of your overall physical health. No single measurement tells the whole story, but together they provide valuable, structured insights.
Rather than focusing on one number in isolation, investors examine several ratios together to assess a company’s financial stability.
Because industries have different business models, capital requirements and growth profiles, ratios are generally most useful when comparing companies within the same or similar sectors.
No single ratio can determine whether a company is a good or bad investment. Instead, these tools help investors organise information and ask better questions.
| Ratio | Formula | What It Measures |
| P/E | Share Price ÷ EPS | Valuation relative to earnings |
| ROE | Net Income ÷ Shareholders’ Equity × 100 | Profit generated from shareholder equity |
| Debt-to-Equity | Total Debt ÷ Shareholders’ Equity | Debt relative to shareholder capital |
| Net Profit Margin | Net Income ÷ Revenue × 100 | Profit retained from revenue |
Four Financial Ratios Used in Fundamental Analysis
1. Price-to-Earnings Ratio
The Price to Earnings ratio, commonly known as the P/E ratio, compares a company’s share price with its earnings per share.
P/E Ratio = Share Price ÷ Earnings Per Share
Think of it this way. Imagine a company earns £5 per share and its stock trades at £100.
P/E Ratio = £100 ÷ £5 = 20
This means investors are willing to pay £20 for every £1 of annual earnings the company generates.
As a general guide:
- Below 10 may indicate weaker growth expectations, industry challenges or possible undervaluation.
- Around 15 to 25 is common for many mature companies.
- Above 30 may reflect strong growth expectations and investor optimism.
However, context matters. A high P/E ratio does not automatically mean a company is overvalued, and a low P/E ratio does not instantly mean it is cheap. Technology companies, for example, often trade at higher valuations than utility or consumer staple businesses.
2. Return on Equity
Return on Equity, or ROE, measures how effectively a company uses shareholders’ capital to generate profits.
ROE = Net Income ÷ Shareholders’ Equity x 100
Suppose shareholders have invested £1 billion into a company, and the business generates £200 million in annual profit.
ROE = £200 million ÷ £1 billion x 100 = 20%
In simple terms, this means the company generates 20 pence of profit for every £1 invested by shareholders.
As a general guide:
- Below 10% may indicate lower profitability and weaker capital efficiency.
- Between 10% and 20% is often viewed as healthy for many companies.
- Above 20% may indicate strong returns, although exceptionally high figures should be examined carefully.
A higher ROE generally suggests that management is using invested capital efficiently. However, excessive borrowing can sometimes artificially inflate this percentage.
3. Debt-to-Equity Ratio
Debt ratios help investors understand how much borrowing a company uses to finance its operations.
One commonly used measure is the Debt-to-Equity ratio.
Debt-to-Equity Ratio = Total Debt ÷ Shareholders’ Equity
Imagine a company has £500 million of debt and £1 billion of shareholders’ equity.
Debt-to-Equity Ratio = £500 million ÷ £1 billion = 0.5
This means the company has 50 pence of debt for every £1 provided by shareholders.
As a general guide:
- Below 0.5 may suggest a strong balance sheet and greater financial flexibility.
- Between 0.5 and 2.0 is relatively common across many industries.
- Above 2.0 may indicate higher financial risk, particularly during periods of economic uncertainty.
Acceptable debt benchmarks vary considerably between industries. Banks and utilities, for example, often operate with more leverage than technology companies.
4. Net Profit Margin
Net profit margin measures how much of a company’s revenue remains as profit after expenses, interest and taxes have been accounted for.
Net Profit Margin = Net Income ÷ Revenue × 100
Suppose a company generates £100 million in revenue and earns £20 million in profit.
Profit Margin = £20 million ÷ £100 million x 100 = 20%
This means the company keeps 20 pence in profit for every £1 of sales it generates.
As a general guide:
- Below 5% may indicate intense competition or limited pricing power.
- Between 10% and 20% is common for many established businesses.
- Above 20% may suggest strong profitability and potential competitive advantages.
Higher margins generally indicate that a company retains a larger proportion of its sales as profit.
Importantly, no ratio should be viewed in isolation. A number that appears attractive on the surface does not always mean a company is fundamentally stronger. For example, an exceptionally high Return on Equity may sometimes be the result of excessive borrowing, while a low Price-to-Earnings ratio could reflect investor concerns about future growth prospects.
Do Financial Ratios Always Tell the Full Story?
No.
Financial ratios are valuable diagnostic tools, but they do not provide all the answers.
They are largely based on historical information, meaning they can provide useful snapshots of the past but cannot predict future performance with certainty.
A company with attractive historical ratios can still face:
- Weak future growth prospects
- Intensifying competition
- Unexpected regulatory changes
- Changes in consumer behaviour
- Poor management decisions
Ratios are also fluid rather than fixed. They change as companies report new earnings, alter their debt levels, repurchase shares or experience changes in profitability.
This is why ratios should be viewed as starting points for deeper research rather than definitive investment answers.
Bottom Line
Financial ratios are among the most widely used tools in fundamental analysis because they help investors evaluate valuation, profitability and financial strength.
The P/E ratio, Return on Equity, debt ratios and profit margins each provide different insights into how a company operates behind its share price.
Although these measures provide valuable financial context, they do not guarantee investment success or eliminate market risk.
The goal is not to search for a single perfect ratio, but to build a broader understanding of a company’s financial position.
Just as doctors rely on several tests to assess a patient’s health, investors often combine multiple ratios to develop a more complete view of a business.
Looking at several measures together can help investors make more informed decisions and avoid relying too heavily on any one number.
The goal is not to search for a single perfect ratio, but to build a broader understanding of a company’s financial position.