P/E Ratio Calculator

What Is the P/E Ratio?

The Price-to-Earnings ratio (P/E) is the most widely used stock valuation metric. It tells you how much investors are willing to pay for each dollar of a company's earnings: P/E = Stock Price ÷ Earnings Per Share (EPS).

A P/E of 20 means investors pay $20 for every $1 of annual earnings. Think of it as: if you bought the entire company at today's price, it would take 20 years of current earnings to recoup your investment (assuming earnings stay constant). Lower P/E suggests cheaper valuation; higher P/E suggests investors expect significant growth.

The S&P 500's historical average P/E is approximately 15-17. In 2026, it has been trading at 20-25 — elevated by historical standards, reflecting strong earnings growth expectations, low interest rate environments, and the dominance of high-growth tech companies in the index. A P/E significantly above or below 15-17 signals that the market is pricing in either optimism or pessimism about future earnings.

Types of P/E Ratios

Trailing P/E (TTM — Trailing Twelve Months): Uses actual earnings from the past 12 months. This is the most commonly reported P/E and the most reliable because it is based on real, reported numbers. When you see "P/E ratio" without qualification, it is usually trailing P/E.

Forward P/E: Uses estimated earnings for the next 12 months (analyst consensus). Forward P/E is always lower than trailing P/E for growing companies because projected future earnings are higher. A stock with 25 trailing P/E and 20 forward P/E: analysts expect 25% earnings growth. Forward P/E is useful for growth companies but depends on analyst estimates, which are often wrong.

Shiller P/E (CAPE — Cyclically Adjusted P/E): Uses the average of the last 10 years of inflation-adjusted earnings. Smooths out business cycle effects and one-time events. The CAPE ratio is the best predictor of long-term (10-year) stock market returns. The S&P 500's current CAPE of approximately 33-36 suggests lower-than-average future returns (historically, CAPEs above 30 have preceded below-average 10-year returns).

How to Use P/E for Investment Decisions

Compare within the same industry: P/E ratios vary enormously by sector. Tech companies average P/E of 25-40; utilities average 12-18; banks average 8-14. Comparing a tech stock's P/E to a utility's is meaningless — compare it to other tech stocks.

Understand why P/E is high or low: A high P/E can mean the stock is overvalued OR that investors expect strong future growth (justified premium). Amazon traded at 100+ P/E for years — seemingly overvalued, but earnings growth eventually justified the price. A low P/E can mean the stock is cheap OR that earnings are expected to decline (value trap).

Use P/E alongside other metrics: P/E alone does not tell you whether to buy or sell. Combine it with: PEG ratio (P/E ÷ earnings growth rate — below 1.0 suggests undervaluation relative to growth), revenue growth, debt levels, free cash flow, and competitive position. A stock with 30 P/E and 35% annual earnings growth (PEG = 0.86) may be cheaper than a stock with 12 P/E and 5% growth (PEG = 2.4).

Negative P/E: Companies with losses have no meaningful P/E (some sources show "N/A" or "negative"). For unprofitable companies, use Price-to-Sales (P/S) or Price-to-Book (P/B) as alternative valuation metrics.

Frequently Asked Questions