The PEG ratio compares P/E with annual EPS growth; examples show how growth horizons, units, and forecast revisions change the result.
The price/earnings-to-growth ratio, or PEG ratio, divides a company’s stated price-to-earnings multiple by a selected annual earnings-growth rate expressed in percentage points. It adds a growth input to P/E comparison, but it does not determine intrinsic value or establish that a particular stock is fairly priced.
A PEG result is meaningful only when the P/E basis, growth measure, forecast horizon, units, and source date are disclosed. Different conventions can produce different PEG ratios for the same company.
12.5 for 12.5%.20x P/E divided by 10% growth is usually calculated as 20 / 10 = 2.0, not 20 / 0.10.1.0 is a rule of thumb in some discussions, not a universal fair-value threshold derived from valuation theory.Under the common percentage-point convention:
Here, g_% is the annual earnings-growth rate in percentage-number form. A decimal rate of g = 0.12 becomes g_% = 12. A rate of 12.5% becomes 12.5, not 0.125; do not round it to a whole number.
For clarity:
Using 0.12 directly in the denominator without multiplying by 100 would produce a number 100 times larger than the usual quoted PEG convention.
Assume a company has:
$60$312%The forward P/E ratio is:
Using 12, not 0.12, in the common PEG convention:
If the growth estimate falls to 8% and the share price and EPS estimate remain unchanged:
The higher ratio reflects less forecast growth for the same P/E. It does not prove that 1.67 is attractive or 2.50 is overvalued. The result still omits the duration, risk, reinvestment, and cash economics of that growth.
In a separate hypothetical forecast, keep the share price at $60. Next-year diluted EPS is $3.00, and Year 4 EPS is $3.993 on the same accounting and per-share basis. There are three annual intervals between Year 1 and Year 4:
Forward P/E is 20x, so PEG is 20 / 10 = 2.00. The cumulative EPS increase is 33.1%, but dividing P/E by 33.1 would produce about 0.60 and incorrectly treat three years of growth as one. The CAGR summarizes the endpoints; it does not require identical growth in each intervening year.
Now reduce the Year 1 EPS forecast to $2.50 while keeping the price, Year 4 forecast, three-year interval, and earnings basis unchanged:
| Input or result | Original forecast | Revised forecast |
|---|---|---|
| Year 1 diluted EPS | $3.00 | $2.50 |
| Year 4 diluted EPS | $3.993 | $3.993 |
| Three-year forecast EPS CAGR | 10.00% | About 16.89% |
| Forward P/E at $60 | 20.0x | 24.0x |
| PEG using unrounded CAGR | 2.00 | About 1.42 |
PEG falls despite the lower near-term earnings forecast. The larger percentage rebound from a smaller base more than offsets the higher P/E in this calculation. That is not evidence that the earnings outlook improved: compare the full forecast path and absolute EPS amounts, not just the new PEG.
State whether P/E is trailing, current-year forecast, next-year forecast, reported, adjusted, or normalized. Confirm that earnings are positive and that price and EPS refer to the same share class and currency.
State whether growth is:
EPS growth is usually the more consistent denominator for an equity P/E because both are per-share measures. Net-income growth can differ from EPS growth when shares are issued or repurchased.
| Variant | P/E input | Growth input | Main concern |
|---|---|---|---|
| Trailing PEG | Trailing P/E | Historical EPS growth | Past growth may not persist |
| Forward PEG | Forward P/E | Forecast EPS growth | Both inputs depend on estimates |
| Mixed PEG | Trailing P/E | Forecast growth | Combines historical earnings price with future growth |
| Normalized PEG | P/E on normalized EPS | Normalized or cycle-adjusted growth | Requires substantial analyst judgment |
None is automatically correct for every use. Comparisons require the same variant, growth horizon, and data date across companies.
A P/E comparison alone does not explicitly display expected growth. PEG can help screen companies with different forecast growth rates and can force the analyst to state the growth assumption behind a valuation comparison.
For example, a 25x P/E may look expensive beside a 15x peer, but the first company’s expected EPS growth may also be higher. PEG summarizes that relationship in one number.
The simplification is also the limitation. Growth does not have a linear one-for-one relationship with justified P/E in a complete valuation model. Required return, payout, return on incremental capital, competitive advantage, leverage, dilution, and growth duration also matter.
The idea that P/E should equal the percentage growth rate produces a PEG of 1.0. It is a heuristic, not a general valuation identity.
Two companies with PEG ratios of 1.0 can have very different values because:
A PEG threshold should therefore be treated as a screening convention, not a buy, sell, or fair-value rule.
| Measure | Inputs | Main question | Important limitation |
|---|---|---|---|
| PEG | P/E and earnings-growth rate | How much P/E is paid per percentage point of stated growth? | Omits growth duration, risk, and reinvestment |
| P/E | Share price and EPS | How much equity price is paid per unit of earnings? | Does not explicitly display growth |
| Earnings Yield | EPS divided by price | What percentage of price is represented by earnings? | Not a cash return or growth measure |
| Discounted Cash Flow | Forecast cash flows and discount rates | What present value follows from explicit assumptions? | Highly sensitive to forecasts and terminal value |
PEG is best used as one relative-value cross-check rather than a substitute for cash-flow, balance-sheet, and business-quality analysis.
1.0 as universal fair value.CFA Institute describes PEG as a relative-valuation tool and explains that justified P/E also depends on growth and required return. FINRA and SEC materials provide estimate and EPS context. These sources do not establish a universal PEG cutoff.
This article provides general financial education. It does not provide personalized investment, valuation, accounting, tax, or legal advice and does not recommend a security, growth estimate, or PEG threshold.