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P/E Ratio, ROE, and the 5 Key Metrics Every Investor Must Know

⏱ 8 min read · Last updated July 2026 · Try Fintiq Free

Every investment decision ultimately comes down to numbers. But not all numbers are created equal. An annual report for a large company like AstraZeneca or Unilever contains hundreds of pages of financial data — revenue, costs, cash flows, debt, equity, dividends, capital expenditure, intangibles, tax provisions, and much more. For a new investor, the volume of information can feel overwhelming.

The good news: you don't need to understand all of it. A relatively small set of financial metrics — perhaps five or six — captures the vast majority of what matters when evaluating a company as an investment. These metrics are the language that professional investors speak. Once you understand them, you can read a company's financial position in minutes rather than hours.

This guide covers the five most important financial ratios for equity investors, with plain-English explanations, the formulas behind them, and UK examples drawn from real FTSE 100 companies.

Why Financial Metrics Matter

Financial metrics allow investors to compare companies that are otherwise incomparable. AstraZeneca is a pharmaceutical giant with revenues exceeding $45 billion. A smaller FTSE 250 company might have revenues of £200 million. Comparing their raw profit figures is meaningless. But comparing their Return on Equity, their Free Cash Flow margin, or their P/E ratio puts them on equal footing — you can assess the quality and valuation of each business relative to its own size and structure.

Metrics also allow you to track a company's progress over time. A P/E ratio of 18 tells you little in isolation. But if that same company had a P/E of 12 three years ago, and the business fundamentals haven't changed significantly, it may suggest the stock has become more expensively valued — and possibly less attractive as an investment.

Finally, metrics expose problems that narrative cannot hide. A CEO's letter to shareholders is always optimistic. The cash flow statement cannot lie in the same way.

Metric 1 — Price-to-Earnings Ratio (P/E)

Formula: P/E Ratio = Share Price ÷ Earnings Per Share (EPS) Example: Share price £4.50, EPS £0.35 P/E = £4.50 ÷ £0.35 = 12.9x

The P/E ratio is the single most widely quoted valuation metric in equity investing. It answers a simple question: how much are investors currently paying for each £1 of the company's annual earnings?

A P/E of 12 means investors are paying £12 for every £1 of profit the company generates each year. A P/E of 30 means they are paying £30 for that same £1 of profit. Neither is automatically good or bad — the interpretation depends entirely on context.

The FTSE 100 as a whole has historically traded at an average P/E of approximately 14–16 times earnings. Individual sectors vary enormously:

SectorTypical P/E RangeReason
Technology / Growth25–50xHigh growth expectations priced in
Consumer Staples15–22xStable, predictable earnings
Financials (Banks)8–12xCyclical, capital-intensive, regulated
Energy7–14xCommodity-linked, volatile earnings
Healthcare18–30xPipeline optionality, pricing power
Utilities12–18xStable but slow-growing earnings

UK Example: Tesco PLC has historically traded on a P/E of around 10–14 times. This reflects its position as a mature UK retailer with moderate and relatively predictable earnings growth. By contrast, RELX PLC — the data analytics and publishing group — has consistently traded on a P/E of 28–35 times, reflecting its high-quality, recurring-revenue business model and strong pricing power. Both are FTSE 100 companies; neither P/E is "wrong" — they reflect entirely different business profiles.

The P/E Trap: a very low P/E ratio can seem like a bargain. Sometimes it is. More often, it signals that the market expects the company's earnings to decline significantly. Always ask: "Why is this stock cheap?" A P/E of 5 on a company whose earnings are falling 30% per year is actually expensive on a forward basis.

For practical screening, use P/E as a relative tool: compare a company's P/E to its sector peers and to its own historical average. A company trading at a discount to both its sector and its own history is worth examining more closely.

Metric 2 — Return on Equity (ROE)

Formula: ROE = (Net Income ÷ Shareholders' Equity) × 100% Example: Net Income £500m, Shareholders' Equity £3,000m ROE = (£500m ÷ £3,000m) × 100% = 16.7%

Return on Equity measures how efficiently a company converts shareholder capital into profit. It is perhaps the single most important metric for assessing the quality of a business.

Think of it this way: if you invested £10,000 in a company and the company generated £1,500 in profit on that investment, your ROE would be 15%. If another company generated only £700 on the same £10,000 investment, its ROE would be 7%. The first company is a far more efficient allocator of capital.

Warren Buffett has consistently cited high and sustainable ROE as one of the defining characteristics of a great business. Berkshire Hathaway's portfolio — Coca-Cola, American Express, Apple — is filled with companies that sustain ROE above 20% over long periods. In the UK, companies like AstraZeneca (ROE consistently above 40%), Diageo (ROE above 30%), and RELX (ROE above 25%) demonstrate what genuinely high-quality businesses look like.

Benchmarks to use:

Warning — The Debt Distortion: ROE can be artificially inflated by high debt. If a company borrows heavily, it reduces the equity base (the denominator), which mechanically increases ROE. A company with ROE of 40% funded mostly by debt is very different from one with 40% ROE and minimal debt. Always check the Debt-to-Equity ratio alongside ROE. This relationship is formalised in the DuPont decomposition, which breaks ROE into three components: profit margin, asset turnover, and financial leverage.

Metric 3 — Debt-to-Equity Ratio

Formula: Debt-to-Equity = Total Financial Debt ÷ Total Shareholders' Equity Example: Total Debt £1,200m, Shareholders' Equity £2,000m D/E = £1,200m ÷ £2,000m = 0.60x

The Debt-to-Equity ratio tells you how a company finances its operations and growth — through shareholders' funds (equity) or through borrowing (debt). A D/E of 0.60 means the company has borrowed £60 for every £100 of shareholder capital. A D/E of 2.0 means it has borrowed £200 for every £100 of equity.

Debt amplifies returns in good times and magnifies losses in bad times. A company with very high debt can face severe distress when earnings fall — as happened to many UK retailers during the COVID-19 pandemic — because debt servicing (interest payments) continues regardless of trading conditions.

Sector context is critical: some sectors structurally carry higher debt because of their business models. UK water companies, for example, borrow heavily to fund infrastructure investment against their regulated, inflation-linked revenue streams. A D/E of 2.0 for Severn Trent is unremarkable; a D/E of 2.0 for a retailer would be deeply concerning.

General benchmarks (for non-financial companies):

Always look at this metric in conjunction with the interest coverage ratio (operating profit divided by interest expense). A company with high debt but strong earnings can service that debt comfortably; a company with high debt and thin margins cannot.

Metric 4 — Revenue Growth

Formula: Revenue Growth = ((Revenue Year 2 - Revenue Year 1) ÷ Revenue Year 1) × 100% Example: Revenue Year 1 = £5.0bn, Revenue Year 2 = £5.4bn Revenue Growth = ((£5.4bn - £5.0bn) ÷ £5.0bn) × 100% = 8.0%

Revenue growth is the lifeblood of a business. Everything else — profits, cash flow, dividends — ultimately depends on a company's ability to grow its sales over time. Without revenue growth, a company must rely entirely on efficiency improvements and cost-cutting to grow earnings, which has hard limits.

When evaluating revenue growth, look for three things:

Consistency Over Time

A company that has grown revenues by 6–10% per year for the past five consecutive years is far more valuable than one that grew 35% one year, contracted 10% the next, grew 20% the year after, and then fell 5%. Consistency of growth suggests structural competitive advantage rather than one-off tailwinds.

Organic vs Acquired Growth

Revenue growth through acquisitions is relatively easy to manufacture but doesn't necessarily create value. Organic revenue growth — selling more of your own products to more customers at higher prices — is the gold standard. Check whether growth is primarily organic or acquisition-driven when reading company reports.

Growth vs Profitability

High revenue growth that comes at the cost of profitability — where a company is selling more but making less on each sale — is not inherently valuable. The best businesses grow revenues while simultaneously maintaining or improving margins.

UK example: Halma PLC, the FTSE 100 safety technology company, has delivered remarkably consistent organic revenue growth of 5–10% annually for over two decades, combined with strong and improving margins. This consistency of growth, not its absolute level, is what makes Halma prized by quality-focused investors.

Metric 5 — Free Cash Flow Margin

Formula: Free Cash Flow = Operating Cash Flow − Capital Expenditure FCF Margin = (Free Cash Flow ÷ Revenue) × 100% Example: Operating Cash Flow £800m, CapEx £150m, Revenue £4,000m FCF = £800m - £150m = £650m FCF Margin = (£650m ÷ £4,000m) × 100% = 16.3%

Free Cash Flow is the cash a business generates after funding the capital expenditure required to maintain and grow its operations. It represents the true "spare" cash available for dividends, share buybacks, debt repayment, or further investment.

FCF is, in the eyes of many professional investors, the most important financial metric of all. Here is why: reported earnings (net income) can be influenced by accounting choices. A company can choose different depreciation schedules, different revenue recognition policies, or different provisions — all of which can make reported profit appear higher or lower than the economic reality. Cash flow, by contrast, is objective. Either money arrived in the bank account, or it did not.

A company with consistently strong FCF can:

FCF margin benchmarks:

UK example: RELX PLC generates FCF margins consistently above 20%, reflecting its asset-light, subscription-driven business model where customers pay annually in advance. This high FCF generation is one of the reasons RELX has been one of the best-performing FTSE 100 stocks over the past decade.

Bonus Metric — EPS Growth Trend

Formula: EPS = Net Income ÷ Weighted Average Shares Outstanding EPS Growth = ((EPS Year 2 - EPS Year 1) ÷ EPS Year 1) × 100%

Earnings Per Share growth measures how much profit is available to each shareholder on a per-share basis. EPS grows when either net income grows, or when the company reduces the number of shares outstanding (through buybacks), or ideally both.

Consistent EPS growth over 3–5 years is one of the clearest signals that a company is genuinely compounding value for shareholders. It means profits are growing faster than dilution — a combination that drives long-term share price appreciation.

Watch for cases where net income grows but EPS does not — this suggests significant share issuance (dilution) is offsetting profit growth. The shareholders' share of the company is being reduced even as the business nominally grows.

How Fintiq Displays All Metrics in One Place

One of the most time-consuming parts of manual fundamental analysis is gathering these metrics. They appear in different sections of annual reports, on different pages of financial databases, and need to be cross-referenced and contextualised. Fintiq aggregates all five metrics above — plus many more — into a single, real-time dashboard for any stock you search.

The Fundamental Screener allows you to filter across all these metrics simultaneously. The individual stock view shows each metric's current value, its 5-year history, its sector percentile ranking, and whether the trend is improving or deteriorating. The composite Quality Score brings them all together into a single 0–100 rating.

This means you can assess a company's key financial metrics in two minutes rather than two hours — and then spend your valuable analytical time on the qualitative questions that data alone cannot answer.

What To Do With These Metrics

Understanding these five metrics is only the beginning. The real skill lies in using them together, in context, to form a view on a company's quality and valuation:

  1. Use the screener to filter for companies with strong metrics across multiple dimensions simultaneously
  2. Read the annual report of any company that passes your screen — focus on the CEO's letter, the risk section, and the cash flow statement
  3. Assess the competitive moat — does the company's high ROE and FCF margin reflect a durable advantage, or is it temporary?
  4. Check the valuation — a great business at a fair price beats a mediocre business at a cheap price
  5. Monitor the trends — metrics that are improving tell a different story from metrics that are deteriorating, even if the absolute levels look similar

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