Deep Dive: What Is the PEG Ratio — How It Combines Price, Earnings, and Growth Into One Valuation Metric
The price-to-earnings (P/E) ratio is the most widely cited valuation metric in investing — but used in isolation, it can be deeply misleading. A stock trading at 47 times earnings looks expensive next to one at 23 times earnings. But what if the first company is growing earnings at 57% annually while the second is growing at 15%? Suddenly the picture inverts. That is exactly the problem the PEG ratio solves. The PEG ratio — short for price/earnings-to-growth — adjusts the P/E ratio by the company's earnings growth rate, giving investors a single number that accounts for both what they are paying and what they are getting in return. Developed by investor Peter Lynch and popularized in his 1989 book *One Up on Wall Street*, the PEG ratio remains one of the most practical tools for comparing growth stocks on a level playing field. With the Federal Reserve cutting rates from 4.33% in August 2025 to 3.64% in January 2026, growth stocks have surged — and so have their P/E ratios. In this environment, PEG becomes especially valuable: it helps investors distinguish between stocks that are genuinely expensive and those that are simply priced for the growth they are delivering.