On this page
What the PEG ratio is
The price-to-earnings ratio tells you how expensive a stock is relative to its profits, but it does not account for growth. The PEG ratio fixes that by dividing the price-to-earnings ratio by the company's expected earnings growth rate. It puts a fast grower and a slow grower on a more even footing.
The thinking is that a company growing profits quickly deserves a higher price-to-earnings ratio than a stagnant one, so dividing by the growth rate reveals whether you are paying a fair price for that growth.
How to read it
A common rule of thumb treats a PEG ratio around 1 as roughly fair value, a ratio below 1 as potentially cheap relative to growth, and a ratio above 1 as potentially expensive. By this logic, a stock with a high price-to-earnings ratio can still look reasonable if its growth is fast enough.
These thresholds are guidelines, not laws. They are a starting point for asking better questions, not a signal to act on by themselves.
💡 The growth number is an estimate:A PEG ratio is only as reliable as the growth forecast behind it, and forecasts are often wrong. Two analysts using different growth assumptions can produce very different PEG ratios for the same stock.
Why it can help
The PEG ratio addresses a real weakness of the price-to-earnings ratio, which can make fast-growing companies look expensive when they may not be. By bringing growth into the picture, it offers a fairer way to compare a quickly expanding company with a mature, slow-growing one.
It is a favorite quick check among growth-oriented investors for exactly this reason. Our guide on growth versus value investing puts the broader style in context.
Its weaknesses
The PEG ratio leans entirely on a growth estimate, and growth is hard to predict. Rapid growth rarely lasts as long as forecasts assume, and a small change in the assumed rate swings the ratio dramatically. It also ignores risk, debt, and the quality of earnings.
Treat the PEG ratio as one useful angle, not a precise valuation. It is best paired with a hard look at how realistic the growth assumption really is.
Frequently asked questions
What is a good PEG ratio?
A common rule of thumb treats a PEG ratio around 1 as fairly valued, below 1 as potentially undervalued relative to growth, and above 1 as potentially expensive. These are guidelines, not strict rules, and they depend entirely on the growth estimate used.
Is the PEG ratio better than the P/E ratio?
It can be more informative for fast-growing companies, because it accounts for growth that the price-to-earnings ratio ignores. But it relies on a growth forecast that may be wrong, so it is not automatically better. The two work best used together.
What growth rate should I use for the PEG ratio?
Investors typically use an estimate of future earnings growth, often over the next several years. Because the result depends heavily on this number, it is worth checking how realistic the assumption is and how the ratio changes under more conservative growth.
What are the limitations of the PEG ratio?
It depends on an uncertain growth forecast, assumes growth continues, and ignores risk, debt, and earnings quality. A small change in the assumed growth rate can swing the ratio significantly, so it is a rough guide rather than a precise valuation.
Related tools and pages
These are for learning. Any calculator here shows example scenarios, not predictions of future prices.
Get the free investing newsletter
Two short emails a week — Wednesday market analysis and Friday investing ideas, written for long-term investors.