Price-to-Earnings Growth (PEG) Ratio: Formula, Meaning & What Is a Good PEG?
Last Updated on 1 month ago by Antony C.
A stock with a P/E ratio of 30 may look expensive compared to another stock with a P/E of 15. But if the first company is growing its earnings three times faster, the comparison becomes less straightforward.
This is where the Price-to-Earnings Growth ratio, or PEG ratio, becomes useful.
- PEG Ratio adds growth to the normal P/E ratio.
- PEG Ratio help us ask if we are paying a reasonable price for the amount of earnings growth we are getting?
PEG Ratio is a fundamental analysis that can provide useful context when comparing companies with different growth rates. However, it relies heavily on earnings estimates, so I would never use it on its own.
Quick Takeaways
- PEG combines P/E with earnings growth, giving us more context than P/E alone.
- A PEG below 1 may suggest attractive valuation relative to growth, while a PEG around 1 is often seen as fairly valued.
- A PEG above 1 may mean investors are paying a premium for the company’s expected growth.
- PEG can be very useful when comparing companies with different growth rates.
- The biggest weakness is that future earnings growth is only an estimate.
- PEG works better for some companies than others. I would be especially careful using it for cyclical companies, very slow-growing businesses, loss-making companies and REITs.
What Is the PEG Ratio?
The PEG ratio, short for Price/Earnings-to-Growth ratio, compares a company’s P/E ratio with its earnings growth rate.
In simple terms:
- P/E tells me how expensive the stock is based on earnings.
- PEG asks whether the company’s growth may justify that valuation.
If you are not familiar with P/E yet, I recommend understanding the Price-to-Earnings Ratio first.
P/E is one of the first valuation ratios I normally look at, but it has an important weakness. It does not directly consider growth, that is where PEG helps us make that distinction.
Why Do Investors Use the PEG Ratio?
The main question PEG tries to answer is:
How much am I paying for the company’s earnings relative to how quickly those earnings are growing?
That makes PEG particularly useful when comparing companies with different growth rates.
A fast-growing company will often trade at a higher P/E because investors expect much higher earnings in the future.
Looking at P/E alone may therefore make many growth companies appear expensive.
PEG adds another piece of information to the picture.
How to Calculate the PEG Ratio
The PEG ratio is actually quite simple to calculate.
PEG Ratio Formula
PEG Ratio = P/E Ratio ÷ Annual EPS Growth Rate
Where:
- P/E Ratio = Share Price ÷ Earnings Per Share
- EPS Growth Rate = How quickly earnings per share are growing
One small thing to remember is that the growth percentage is normally entered as the percentage number.
So if earnings are expected to grow by 20%, we use 20, not 0.20, in the standard PEG calculation.
Simple PEG Ratio Example
Let’s say Company ABC has:
- P/E ratio: 20
- Expected EPS growth: 20% per year
The calculation would be:
- PEG = 20 ÷ 20
- PEG = 1.0
A PEG of around 1 is commonly interpreted as the stock’s valuation being roughly in line with its expected growth rate.
Now imagine the same company has a P/E of 20 but earnings are only expected to grow by 10%.
- PEG = 20 ÷ 10
- PEG = 2.0
The stock hasn’t changed.
Its P/E hasn’t changed.
But once we take slower expected growth into account, the valuation suddenly looks much more expensive.
This is why I find PEG useful.
Forward PEG vs. Trailing PEG
This is one part of PEG that can become confusing because different websites may show different numbers for the same company.
There are generally two ways of looking at PEG.
| Type | P/E Used | Growth Used | What It Tells Us |
|---|---|---|---|
| Trailing PEG | Historical P/E | Historical earnings growth | How valuation compares with past growth |
| Forward PEG | Forward P/E | Expected future earnings growth | How valuation compares with expected growth |
For forward PEG, analysts may use earnings estimates for the next year or even expected annual growth over several years.
Fidelity, for example, describes PEG using projected EPS growth, while Schwab notes that PEG can be calculated using either historical or forward-looking figures.
This means two platforms can show different PEG ratios without either one necessarily being wrong.
What matters is understanding what numbers they are using.
I also try to keep the calculation consistent:
- Trailing P/E → historical earnings growth
- Forward P/E → expected future earnings growth
Mixing a forward valuation with an unrelated historical growth number can give us a PEG that does not really tell us much.
What Is a Good PEG Ratio?
You will often see investors use 1.0 as the basic reference point for PEG.
Here is the simple way to think about it:
| PEG Ratio | General Interpretation |
|---|---|
| Below 1.0 | May be attractively valued relative to its growth |
| Around 1.0 | Valuation may be roughly in line with expected growth |
| Above 1.0 | Investors may be paying a premium for growth |
| Negative | Normal PEG interpretation usually becomes less useful |
Both Schwab and Fidelity describe 1.0 as a commonly used reference point, although the actual meaning still depends on the company, industry and assumptions being used.
Let’s look at each one.
PEG Ratio Below 1
A PEG below 1 is generally considered attractive.
For example:
- P/E = 15
- Expected growth = 20%
- PEG = 0.75
The company appears to be trading at a relatively low valuation compared with its expected growth.
But I would be careful about immediately calling this stock undervalued.
A low PEG could also happen because the market does not believe the company’s growth forecast will last.
That is why a PEG below 1 should make us interested enough to investigate further, not automatically make us invest.
PEG Ratio Around 1
A PEG around 1 is often considered fairly valued relative to growth.
For example:
- P/E = 20
- Growth = 20%
- PEG = 1.0
The valuation and growth rate roughly match according to this simple rule.
Again, it does not mean the stock is definitely fairly valued.
It is just a useful reference point.
PEG Ratio Above 1
A PEG above 1 suggests investors may be paying a premium for the company’s growth.
For example:
- P/E = 30
- Growth = 15%
- PEG = 2.0
That does not automatically make the stock bad.
There may be good reasons investors are willing to pay more, such as:
- Strong competitive advantages
- Consistent earnings
- High profit margins
- Strong balance sheet
- Very predictable business
- Expectations of faster future growth
The number gives us a reason to ask more questions.
What Does a Negative PEG Ratio Mean?
A negative PEG can appear when the company has negative earnings or declining earnings growth.
At this point, the normal PEG rules largely break down.
I would not look at a PEG of -0.5 and think it is somehow “better” than a PEG of 0.8.
A negative number usually means we need to step away from the simple PEG framework and understand what is actually happening with the company’s earnings. Schwab similarly notes that negative PEG readings can result from losses or declining earnings.
Why PEG Can Give You a Clearer Picture Than P/E
This is probably the biggest reason I like PEG.
Let’s compare two companies.
| Company A | Company B | |
|---|---|---|
| P/E Ratio | 30 | 20 |
| Expected EPS Growth | 30% | 10% |
| PEG Ratio | 1.0 | 2.0 |
If I only look at P/E, Company B seems cheaper.
I am paying 20 times earnings instead of 30.
But PEG gives me another perspective.
Company A is expected to grow earnings much faster. Once we adjust the valuation for that growth, Company A has a PEG of 1 compared with Company B’s PEG of 2.
Suddenly, the company with the higher P/E may actually look more reasonably valued relative to its growth.
This is exactly why P/E alone can sometimes give us an incomplete picture. Schwab also notes that PEG can help investors compare companies with different growth rates and check whether a higher P/E may be supported by stronger growth.
For me, this does not mean PEG replaces P/E.
I see it more as the next question to ask after looking at P/E.
When Is the PEG Ratio Most Useful?
PEG works better in some situations than others.
I find it most useful when the company:
- Is already profitable
- Has positive earnings growth
- Has reasonably predictable earnings
- Has a meaningful growth rate
- Can be compared with similar businesses
- Has a P/E that may look high because of its expected growth
This is why PEG can be particularly useful when comparing profitable growth companies.
However, there are also several situations where I would be much more careful.
Which Types of Companies Are Less Suitable for PEG?
| Company Type | PEG Usefulness | Why |
|---|---|---|
| Profitable growth company | More useful | Growth provides useful context for P/E |
| Mature slow-growth company | Use cautiously | Very small growth rates can make PEG unusually high |
| Cyclical company | Use cautiously | Earnings can rise and fall sharply |
| Loss-making company | Usually unsuitable | P/E itself becomes difficult to use |
| Extremely high-growth company | Use cautiously | Very high growth may not be sustainable |
| REIT | Usually not my first choice | Other property and distribution metrics may be more meaningful |
Schwab similarly highlights mature, cyclical and extremely high-growth businesses as situations where PEG can give misleading signals.
What About REITs?
As a dividend investor, REITs are something I look at quite often.
But PEG would normally not be one of my first ratios when analysing a REIT.
The reason is quite simple.
PEG relies on P/E and earnings per share. For REITs, traditional accounting earnings can be affected by property depreciation and other accounting items that may not fully reflect the performance of the underlying property portfolio.
This is one reason measures such as Funds From Operations (FFO) are commonly used when analysing REIT operating performance. Nareit specifically developed FFO to address some of the limitations caused by real-estate depreciation under normal accounting rules.
Depending on the REIT and market, I would rather spend more time looking at things such as:
- Distribution per unit
- FFO or AFFO where applicable
- NAV
- Gearing and debt
- Interest coverage
- Occupancy
- Rental growth
- Distribution sustainability
PEG is not useless in every REIT situation, but it would not be my main valuation tool.
Limitations of the PEG Ratio
PEG solves one weakness of P/E.
Unfortunately, it introduces another big one.
Growth.
More specifically, whether that growth number can actually be trusted.
1. Future Growth Is Only an Estimate
If I calculate a forward PEG, I am using expected earnings growth.
But nobody knows exactly what a company’s earnings will be three or five years from now.
- Analysts can be too optimistic.
- Management can miss its targets.
- Competition can become stronger.
- Costs can rise.
- Consumer behaviour can change.
The PEG ratio is only as reliable as the growth rate we put into it.
2. Trade Wars, Recessions and Black Swan Events Can Change Everything
This is something investors should never forget.
We may build our entire PEG calculation around expectations that a company will grow earnings by 15% a year.
Then something unexpected happens.
It could be:
- A trade war
- A recession
- A financial crisis
- A pandemic
- A geopolitical conflict
- New regulation
- A sudden disruption to the company’s industry
Suddenly that 15% forecast may no longer make sense.
The PEG ratio itself did not fail.
The assumptions behind the PEG changed.
That is why I am especially careful about relying too heavily on forward PEG during uncertain periods.
3. Different Growth Estimates Can Give Very Different PEG Ratios
Suppose a company’s P/E is 20.
- If I expect 10% growth: PEG = 2.0
- If another analyst expects 15%: PEG = 1.33
- If someone else expects 20%: PEG = 1.0
Same stock. Same P/E. Very different PEG.
This is why I always want to know where the growth number came from.
4. Very Low or Very High Growth Can Distort PEG
PEG becomes less useful at the extremes.
A mature company growing earnings by only 2% may show a very high PEG even though the business itself is stable and profitable.
On the other hand, a company growing at 80% may show an amazingly low PEG.
But can that company really continue growing at 80% for years? Maybe. Maybe not.
A good-looking PEG based on unrealistic growth assumptions can give us false confidence.
5. PEG Does Not Tell Us About Debt or Cash Flow
This is another major weakness.
Imagine two companies both have:
- P/E of 20
- Growth of 20%
- PEG of 1
Their PEG ratios are identical.
But Company A may have almost no debt and produce strong free cash flow.
Company B may need to borrow heavily and spend huge amounts of money just to maintain the same growth.
Those are very different businesses.
PEG will not tell us that.
Schwab specifically points out that companies with similar EPS growth may need very different amounts of investment and debt, which is why looking at measures such as free cash flow can provide useful additional context.
6. PEG Does Not Measure Business Quality
This may be the most important limitation of all.
PEG can tell us something about valuation relative to growth.
It cannot tell us whether the company is actually a good business.
PEG does not directly tell us about:
- Competitive advantage
- Management quality
- Debt
- Cash flow
- Profit margins
- Dividend sustainability
- Industry risks
- Balance sheet strength
So I would never buy a stock just because I see a PEG of 0.7.
- The number gets my attention.
- Then the research begins.
How I Use PEG When Analysing a Stock
I like keeping fundamental analysis simple.
When PEG is relevant, I generally think about it in this order:
P/E → Growth → PEG → Check the assumptions → Compare peers → Check the business
1. Look at the P/E
First, I want to understand what investors are currently paying for the company’s earnings.
2. Look at Earnings Growth
Next, I want to know whether earnings are actually growing.
More importantly, I want to understand whether that growth looks sustainable.
3. Check the PEG
PEG gives me a quick way to put the P/E and growth together.
4. Check the Growth Assumption
This is important.
Where did the growth estimate come from?
Is it based on:
- Historical growth?
- Analyst forecasts?
- Management guidance?
- One unusually good year?
The more unrealistic the growth assumption, the less useful the PEG becomes.
5. Compare Similar Companies
I prefer comparing PEG with businesses in the same industry rather than looking at the number completely on its own.
Fidelity also recommends comparing a company’s PEG with its industry and the broader market for better context.
6. Look at the Rest of the Business
Finally, I still want to understand the company itself.
As a dividend investor, that may include looking at:
- Earnings
- Free cash flow
- Debt
- Dividend payout
- Dividend growth
- Balance sheet strength
- Business outlook
PEG is a tool.
It is not the entire analysis.
PEG Ratio vs. P/E Ratio: Which Is Better?
If I had to choose purely for understanding valuation relative to growth, PEG gives me more information.
But I would not throw away P/E.
| P/E Ratio | PEG Ratio | |
|---|---|---|
| Looks at earnings | Yes | Yes |
| Includes growth | No | Yes |
| Simple to calculate | Very simple | Simple |
| Depends heavily on forecasts | Less | More |
| Useful for comparing growth companies | Limited | More useful |
| Works well for every company | No | No |
I see the two metrics as working together.
- P/E tells me how much I am paying for earnings.
- PEG helps me understand whether growth may justify that price.
So rather than asking whether PEG or P/E is better, I think the more useful question is:
What is the P/E not telling me that PEG may help me understand?
That is where PEG becomes useful.
Here’s My Thoughts on the PEG Ratio
I think the PEG ratio is one of the more useful valuation ratios that does not get talked about as much as P/E.
The main reason is simple.
It takes something P/E ignores and puts it directly into the calculation: earnings growth.
A company with a high P/E may not be as expensive as it first appears if earnings are growing quickly. At the same time, a low-P/E company may not be as cheap as it looks if earnings growth is weak.
PEG helps me see that difference.
But I would never stop at the PEG ratio.
The growth rate may be wrong. Economic conditions may change. The company may have too much debt. Cash flow may be weak. The business itself may simply not be very good.
For me, PEG is best used as a second check after P/E, helping me decide whether the valuation deserves a closer look.
Frequently Asked Questions (FAQs) on P/E Ratio
Join 900+ BUDDIES who are growing their wealth with our weekly Income Newsletter
Antony C. is a Singaporean dividend investor focused on building passive income through REITs, ETFs, and Dividend Stocks. With 15+ years of experience investing in Singapore, Hong Kong, and China markets, he founded IncomeBuddies.com to share practical wealth-building strategies tested in his own portfolio since 2008. His expertise has been featured in Yahoo Finance, Nasdaq, and NFAA, and he’s the published book author of "Start Small, Dream Big".