P/E vs. PEG Ratio: Which Valuation Metric Should You Trust?
The price-to-earnings (P/E) ratio is the most quoted number in investing — and also the most misused. Understanding how it relates to the PEG ratio is one of the fastest ways to upgrade your analysis.
What the P/E ratio actually measures
The P/E ratio is simply:
Share price ÷ earnings per share
A P/E of 20 means investors pay $20 for every $1 of annual earnings. As a rough guide, a P/E below 25 is reasonable for most companies. But there's a catch: a low P/E can signal a bargain or a business in decline, and a high P/E can signal hype or a company growing fast enough to justify it.
The P/E alone can't tell those apart.
Why the PEG ratio fixes this
The PEG ratio divides the P/E by the expected earnings growth rate:
PEG = P/E ÷ earnings growth (%)
A PEG below 1.0 is often considered undervalued; below 2.0 is still acceptable. By folding growth into the equation, PEG explains why a company with a P/E of 40 can be cheaper than one with a P/E of 15 — if the first is growing three times as fast.
A quick example
| Company | P/E | Growth | PEG | | --- | --- | --- | --- | | Slow & Co. | 15 | 5% | 3.0 | | Fast Inc. | 40 | 35% | 1.1 |
On P/E alone, Slow & Co. looks cheaper. On PEG, Fast Inc. is clearly the better value relative to its growth.
How to use them together
- Use P/E as a first sanity check on price.
- Use PEG to judge whether that price is justified by growth.
- Be skeptical of PEG when growth estimates are unreliable — for cyclical or turnaround companies, the denominator can be misleading.
Stoxly checks both the P/E and PEG ratios automatically as part of its 10-point analysis.
This article is for educational purposes only and is not financial advice.
For educational purposes only — not financial advice.