# P/E and Forward P/E

> The P/E ratio compares a stock's price with its earnings. Learn trailing vs forward P/E, earnings yield, what high or low P/E means and the ratio's limits.

Source: https://learn.tradelabsai.com/fundamentals/p-e-and-forward-p-e/  
Track: Fundamental Analysis · Level: Intermediate · Updated: 2026-10-03  
Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice.  
Cite as: TradeLabs Learn, "P/E and Forward P/E", https://learn.tradelabsai.com/fundamentals/p-e-and-forward-p-e/

The price to earnings ratio (P/E) is the most widely quoted valuation measure. It shows how many dollars investors pay for each dollar of a company's annual earnings. A P/E of 20 means the stock costs 20 times its earnings per share. The forward P/E uses expected earnings instead of past earnings. P/E ratios are simple and useful for comparing similar companies, but they can mislead when earnings are depressed, inflated or distorted by accounting.

## The formulas

```
P/E = share price / earnings per share
earnings yield = EPS / share price = 1 / P/E
```

| Version | Earnings used | Notes |
|---|---|---|
| Trailing P/E (TTM) | Last 12 months of actual EPS | Based on known results |
| Forward P/E | Analysts' estimated EPS for the next 12 months or fiscal year | Reflects expectations; estimates can be wrong |
| Shiller CAPE | Price / average inflation adjusted earnings over 10 years | Used for whole markets; smooths the cycle |

## Worked example

**Example: Trailing vs forward P/E**
A stock trades at $90. Its EPS over the last four quarters was $3.00; analysts expect $4.00 next year.

- Trailing P/E = 90 / 3.00 = 30.
- Forward P/E = 90 / 4.00 = 22.5.
- Earnings yield (forward) = 4.00 / 90 ≈ 4.4%.

If the company grows into its estimates, the stock "gets cheaper" on a P/E basis. If estimates are cut to $3.20, the forward P/E rises to about 28. See [Guidance and Earnings Revisions](https://learn.tradelabsai.com/fundamentals/guidance-and-earnings-revisions/).

## What a high or low P/E can mean

| P/E | Possible explanations |
|---|---|
| High | Strong expected growth, high quality, low risk, temporarily depressed earnings, or overvaluation |
| Low | Slow growth, high risk, cyclical peak earnings, accounting concerns, or undervaluation |

A low P/E is not automatically a bargain, and a high P/E is not automatically a bubble.

## Typical P/E levels

The S&P 500's long run average trailing P/E has been roughly 15 to 17, though it has spent much of the past two decades higher. Growth sectors such as technology usually trade at higher P/Es than utilities, banks or energy companies. Compare a company's P/E with its own history, its peers and its growth rate. See [Comparable Companies and Precedent Transactions](https://learn.tradelabsai.com/fundamentals/comparable-companies/) and [PEG Ratio](https://learn.tradelabsai.com/fundamentals/peg-ratio/).

## The cyclical trap

For cyclical businesses such as automakers, chipmakers and commodity producers, P/E can be lowest at the peak of the cycle, when earnings are temporarily high, and highest at the bottom, when earnings collapse. Buying cyclicals on a low P/E at the peak can be costly. Many analysts use mid cycle or normalised earnings instead. See [Business and Economic Cycles](https://learn.tradelabsai.com/macro/business-and-economic-cycles/).

## Limits of P/E

- **Negative earnings:** P/E is meaningless for loss making companies.
- **Debt is ignored:** two companies with the same P/E can have very different debt loads. EV/EBITDA accounts for debt. See [EV/EBITDA and EV/Sales](https://learn.tradelabsai.com/fundamentals/ev-ebitda-and-ev-sales/).
- **Accounting distortions:** one off gains, impairments and adjusted figures. See [Earnings Quality and Cash Conversion](https://learn.tradelabsai.com/fundamentals/earnings-quality/).
- **Buybacks** raise EPS and lower P/E without improving the business. See [Buybacks](https://learn.tradelabsai.com/fundamentals/buybacks/).
- **Interest rates:** higher rates generally justify lower P/E ratios, since future earnings are discounted more heavily.

## P/E and interest rates

The earnings yield can be compared with bond yields. When the S&P 500's forward earnings yield is 5% and the 10 year Treasury yields 4.5%, the gap (the equity risk premium proxy) is small, suggesting stocks offer limited extra return for their risk. This comparison is sometimes called the Fed model, though its usefulness is debated.

## Frequently asked questions

### What is a P/E ratio?

The share price divided by earnings per share, showing how much investors pay for each dollar of earnings.

### What is the difference between trailing and forward P/E?

Trailing P/E uses the last 12 months of actual earnings; forward P/E uses analysts' estimates of future earnings.

### What is a good P/E ratio?

It depends on growth, risk, industry and interest rates. Compare a stock's P/E with its peers, its own history and its growth rate rather than using a single number.

Next, adjust P/E for growth with the [PEG Ratio](https://learn.tradelabsai.com/fundamentals/peg-ratio/).

## Continue learning

- Next lesson: [PEG Ratio](https://learn.tradelabsai.com/fundamentals/peg-ratio/)
- Previous lesson: [Valuation Basics](https://learn.tradelabsai.com/fundamentals/valuation-basics/)
- Related: [Valuation Basics](https://learn.tradelabsai.com/fundamentals/valuation-basics/): Valuation estimates what a business is worth. Learn intrinsic vs relative valuation, the main multiples, how growth and risk affect value and common mistakes.
- Related: [PEG Ratio](https://learn.tradelabsai.com/fundamentals/peg-ratio/): The PEG ratio divides P/E by expected earnings growth to compare growth stocks. Learn the formula, how to interpret it, worked examples and its important limits.
- Related: [Net Income and EPS](https://learn.tradelabsai.com/fundamentals/net-income-and-eps/): Net income is profit after all costs; EPS divides it by shares. Learn basic vs diluted EPS, GAAP vs adjusted EPS, buyback effects and how traders use EPS.
- Related: [Comparable Companies and Precedent Transactions](https://learn.tradelabsai.com/fundamentals/comparable-companies/): Comparable company analysis values a business using the multiples of similar companies. Learn how to pick peers, build a comps table and adjust for differences.
- Related: [Earnings Quality and Cash Conversion](https://learn.tradelabsai.com/fundamentals/earnings-quality/): Earnings quality asks whether reported profits are real, repeatable and backed by cash. Learn accruals, warning signs, the Beneish model and famous frauds.