How It Works
The formula is straightforward:
PEG = P/E ratio ÷ expected earnings growth rate (%)
Start with the P/E ratio — the share price divided by earnings per share. Then divide that number by the company's projected annual earnings growth rate, expressed as a percentage without the percent sign.
Take Alphabet (GOOGL) as an example. If GOOGL trades at a P/E of around 22 and analysts expect earnings to grow at roughly 15% per year, the PEG ratio works out to approximately 22 ÷ 15 = 1.47. That single number now carries more information than the P/E alone, because it reflects what investors are paying per unit of expected growth.
The growth rate used is typically a forward-looking estimate — often a 3-to-5-year consensus forecast from analysts — though some versions use historical growth instead. It is worth knowing which input a given source is using, because the two can produce very different results.
How to Read It
The most widely cited rule of thumb is that a PEG of 1.0 suggests a stock is priced in line with its growth. A PEG below 1 is often flagged as noteworthy because it implies the market may not be fully pricing in the expected growth — though this can also signal that the market doubts those growth estimates. A PEG above 1 indicates investors are paying a premium over the implied growth rate, which is common for companies with strong competitive moats or consistent execution records.
Sector context matters a great deal here. Mature, slow-growing industries like utilities or consumer staples routinely carry lower PEG ratios than high-growth technology companies, where elevated multiples are the norm. Comparing PEG ratios across sectors without adjusting for this can be misleading.
Where to Find It on Quantify
The PEG ratio is displayed directly on Quantify stock pages alongside other key valuation metrics, making it easy to see in context. You can explore Alphabet's current figures — including its P/E, forward growth estimates, and PEG — on the GOOGL stock page on Quantify. Having all these numbers in one place makes it straightforward to compare the PEG against sector peers without jumping between sources.
Common Mistakes
Treating the growth estimate as fact. The PEG ratio is only as reliable as the earnings growth forecast plugged into it. Analyst estimates can be optimistic, especially for cyclical businesses or companies in fast-changing industries. A low PEG built on an aggressive growth assumption can be far less meaningful than it appears.
Using it in isolation. The PEG ratio says nothing about a company's debt levels, profit margins, cash flow quality, or competitive position. Analysts use it as one lens among many — a starting point for deeper investigation, not a standalone verdict on whether a valuation is justified.