Fundamentos

P/E Ratio Explained: What It Is, How to Use It & 3 Costly Myths

Equipo MBWe9 de abril de 202612 min read

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Infographic: P/E Ratio — A Guide for Smart Investors

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The P/E Ratio Explained: What Most Investors Get Wrong

The most quoted metric in finance — and probably the most misunderstood. Why can a P/E of 60 be cheaper than a P/E of 8?

What Is the P/E Ratio (Price-to-Earnings Ratio)?

The P/E ratio (Price-to-Earnings Ratio) is the most widely used valuation multiple in equity analysis. It measures how much investors are willing to pay for every dollar of earnings a company generates.

P/E = Price per Share / Earnings per Share (EPS)

A P/E of 15x means you pay €15 for every €1 of annual earnings

The formula looks simple, but the P/E is not an arbitrary number. It reflects three things about a company:

Growth: The faster earnings grow, the more investors are willing to pay. That's why tech companies command premium multiples.

Risk: A riskier company — high debt, cyclical sector — trades at a lower P/E because investors demand a discount for uncertainty.

Earnings distribution: Companies that pay out a high proportion of earnings as dividends rather than reinvesting tend to trade at lower P/E multiples.

This is why P/E ratios vary so widely across sectors and companies. It's not that some are "expensive" and others "cheap" — the market assigns a different multiple based on each company's growth profile and risk characteristics.

Three Variants You Need to Distinguish

Trailing P/E (TTM)

Last 12 months of reported earnings. Backward-looking.

Forward P/E

Analyst estimates for the next 12 months. Forward-looking.

Shiller CAPE (P/E 10)

10-year inflation-adjusted average. Smooths out cycles.

For growth companies, Forward P/E is usually the more relevant metric because it captures market expectations. To assess broad market valuation, Shiller's CAPE is the standard (historical average: ~16x; post-2010: ~22x).

The 3 P/E Myths That Cost Investors Money

These are the three most common misinterpretations — and the ones that do the most damage to portfolios.

Myth

"Low P/E = cheap stock." Many investors hunt for low P/E ratios believing they signal opportunity.

Reality

A low P/E typically reflects low growth expectations, elevated risk, or declining earnings. NVIDIA at 60x can be cheaper than Santander at 6x once you adjust for growth — PEG 0.27 vs 0.75.

Myth

"You can compare P/E ratios across sectors." If a tech company trades at 30x and a bank at 10x, the bank is cheaper.

Reality

Every sector has structurally different P/E ranges driven by differences in growth, capital intensity, and risk. Technology: 25–40x. Financials: 8–15x. Cross-sector comparisons are apples to oranges.

Myth

"Negative P/E = bad company." If earnings are negative, the P/E is meaningless and the company isn't worth considering.

Reality

A negative P/E can signal a company in investment mode (Amazon was unprofitable until 2003), a cyclical trough (energy names during oil downturns), or one-time charges. The P/E ratio simply doesn't work with negative or near-zero earnings.

P/E by Sector: Every Industry Has Its Range

Each sector's structure — growth trajectory, regulatory environment, capital intensity — determines a typical P/E range. Knowing these ranges is the first step to avoiding cross-sector comparison traps.

Typical P/E by Sector (S&P 500)

Sector	Typical P/E	Why
Technology	25 – 40	High growth, scalable, asset-light
Healthcare	20 – 35	Innovation pipeline, patents as moat
Financials	8 – 15	Regulated, cyclical, leverage-dependent
Utilities	15 – 20	Stable, regulated, low growth
Energy	8 – 15	Cyclical, commodity-dependent
Consumer Staples	20 – 25	Defensive, predictable cash flows

Comparing a tech company's P/E to a bank's is apples to oranges. Always compare within the same sector.

Case Study: Who Is More Expensive — NVDA or Santander?

NVIDIA trades at a trailing P/E of ~65x. Banco Santander trades at ~6.5x. Intuition says Santander is 10 times cheaper. But the data tells a different story once you factor in growth.

NVDA vs Banco Santander

NVDA's Trailing P/E is ~10x higher than Santander's, but its PEG is ~3x lower. Growth changes everything. Market data updated daily.

NVIDIA's PEG (~0.27) is a fraction of Santander's (~0.75). Growth-adjusted, NVIDIA is significantly "cheaper" despite a P/E that is 10x higher. The lesson: a P/E ratio without context is a number without meaning.

When the P/E Breaks Down — 5 Limitations to Know

Earnings manipulation: EPS can be legally managed through accounting decisions — depreciation methods, revenue recognition timing, share buybacks.

Cyclical distortion: At cyclical peaks, EPS is inflated → P/E looks low → value trap. The opposite holds at troughs.

Ignores leverage: Two companies with the same P/E but different debt loads have very different risk profiles. EV/EBITDA corrects for this.

Non-recurring items: An extraordinary write-down or asset sale can make any given quarter's P/E meaningless.

Ignores growth: P/E alone says nothing about future earnings growth. The PEG ratio (P/E / growth rate) partially addresses this.

Interactive Calculator: P/E and PEG

Enter the share price, earnings per share, and expected growth rate to calculate the P/E and PEG ratios. Per Peter Lynch, a PEG below 1.0 suggests the stock may be undervalued relative to its growth.

P/E & PEG Calculator

Share Price (€)

Earnings per Share — EPS (€)

Annual EPS Growth (%)

P/E

65.0x

PEG

2.17

Potentially overvalued

PEG < 1.0 = potentially undervalued (Peter Lynch). PEG assumes a linear P/E-to-growth relationship and breaks down at extremes.

Key Takeaways

Never use P/E in isolation. Always combine it with the growth rate (PEG), sector context, and earnings quality.

Compare within the same sector, never across sectors. A 25x P/E in technology and a 25x P/E in banking mean very different things.

Prefer Forward P/E for growth companies and Trailing P/E for mature, stable businesses.

Be skeptical of very low P/E ratios — they often signal a declining business, a cyclical peak, or a value trap.

To assess the overall market, use Shiller's CAPE — not the P/E of any individual stock.

See how we apply the P/E ratio in our NVDA report

Every company analyzed across 12 dimensions: valuation, growth, moat, risk, momentum and more.

View NVDA report View plans

Sources

1.Benjamin Graham — Security Analysis (1934). The foundational text on fundamental analysis and multiple-based valuation.
2.Public financial databases — Real-time financial data. Company profiles, TTM metrics, and analyst estimates.
3.S&P Global — Sector P/E ranges for the S&P 500 (2024–2025 data).
4.Peter Lynch — One Up on Wall Street (1989). Popularized the PEG ratio as a growth-adjusted valuation tool.
5.Robert Shiller — Irrational Exuberance (2000). CAPE / Shiller P/E as a market-wide valuation indicator.

Educational compilation for My Best Wealth. Data from Bloomberg, FRED, SEC filings, and public financial databases (2024–2026). This content is educational — it does not constitute financial advice.

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P/E Ratio Explained: What Most Investors Get Wrong

The P/E ratio is the most widely used metric in finance — and the most misunderstood. Learn how to use it properly, when it lies, and why comparing P/E across sectors is a classic mistake.

This article is for educational and informational purposes only. It does not constitute financial advice or personalized investment recommendations. Investing involves risks.

The P/E Ratio Explained: What Most Investors Get Wrong

What Is the P/E Ratio (Price-to-Earnings Ratio)?

Three Variants You Need to Distinguish

The 3 P/E Myths That Cost Investors Money