PEG Ratio Calculator

PEG Ratio Calculator — A Free Tool to Check If a Growth Stock Is Actually Worth the Price

A stock can look expensive and cheap at the same time, depending on how you measure it. That's the whole problem with using the P/E ratio on its own — it tells you the price you're paying for a dollar of earnings, but it says nothing about how fast those earnings are growing. Two companies can trade at the exact same P/E of 25, and one of them can be a bargain while the other is badly overpriced. The difference comes down to growth, and that's exactly what the PEG ratio is built to capture.

This calculator takes the two numbers that matter — the P/E ratio and the expected earnings growth rate — and turns them into one simple figure you can use to judge value in seconds. Enter a P/E ratio directly, or let the tool work it out from the stock price and earnings per share. Add your growth rate estimate, and you'll instantly see the PEG ratio, how it compares to other stocks in the same sector, and the exact growth rate the company would need to hit for the stock to be considered fairly priced.

What Is the PEG Ratio? A Plain-English Explanation

PEG stands for Price/Earnings-to-Growth. It's a valuation number that adjusts the familiar P/E ratio for how quickly a company's profits are expected to grow. Instead of just asking 'how much am I paying for $1 of earnings today', the PEG ratio asks 'how much am I paying for $1 of earnings, given how fast those earnings are growing?'

The formula is short: PEG Ratio = P/E Ratio ÷ Annual EPS Growth Rate (%)

So if a stock trades at a P/E of 20 and analysts expect its earnings to grow 20% a year, the PEG ratio is 20 ÷ 20 = 1.0. If another stock also trades at a P/E of 20 but is only expected to grow earnings by 5% a year, its PEG ratio is 20 ÷ 5 = 4.0. Same P/E, completely different story. The first stock is priced in line with its growth. The second one looks expensive once growth is taken into account.

The metric was popularized by legendary Fidelity fund manager Peter Lynch, who used a PEG ratio near 1.0 as a rough rule of thumb for a fairly priced growth stock in his book 'One Up On Wall Street'. It has since become one of the most widely used shortcuts for comparing growth stocks to their price tags.

How to Use This PEG Ratio Calculator — Step by Step

Step 1 — Choose how you want to enter the P/E ratio. If you already know the stock's P/E, pick 'P/E Ratio' and type it in directly. If you'd rather work it out yourself, pick 'Price & EPS' and enter the current share price along with the trailing twelve-month earnings per share. The calculator divides the two for you automatically.

Step 2 — Enter the expected annual EPS growth rate. This is the number that makes the whole calculation meaningful, so take a moment to get it right. You can use the company's own guidance, an analyst consensus estimate (usually available on any major finance website), or a historical 3-to-5-year average growth rate if you'd rather look backward instead of forward.

Step 3 — Read the PEG ratio and its rating. The calculator instantly shows whether the stock looks undervalued, fairly valued, or overvalued relative to its growth, along with a visual spectrum so you can see exactly where it sits.

Step 4 — Check the sector comparison. A PEG of 2.0 might be expensive for an energy company but perfectly normal for a consumer staples stock. Pick the closest sector to see how the PEG stacks up against typical industry levels.

Step 5 — Use the reverse target calculator. Set a target PEG ratio — 1.0 is the classic Peter Lynch benchmark — and the tool tells you exactly what growth rate the company needs to deliver for the current price to be considered fair. This flips the question around: instead of 'is this cheap?' you're asking 'how much does this company actually need to grow to justify what I'm paying?'

Step 6 — Review the growth sensitivity table. Growth forecasts are never guaranteed, so this table shows what happens to the PEG ratio if actual growth comes in a few points higher or lower than expected. It's a quick way to see how sensitive your conclusion is to the growth number you picked.

What Is a Good PEG Ratio? The Full Breakdown

This is one of the most common questions investors search for, and the honest answer is: it depends on the sector and the quality of the growth estimate, but there are widely accepted general ranges.

Below 0.5 — Deeply Undervalued: The market is pricing in barely any of the company's forecast growth. This can be a genuine bargain, but it's also worth double-checking the growth number isn't wildly optimistic, since an unrealistic estimate will make almost any stock look cheap on paper.

0.5 to 1.0 — Undervalued: This is the range most often associated with attractive growth stocks. A PEG under 1.0 is the classic Peter Lynch signal that a stock may be priced below what its growth rate would justify.

1.0 to 1.5 — Fairly Valued: The stock's price and its growth rate are roughly in balance. Not a screaming bargain, but not expensive either — a reasonable price for what you're getting.

1.5 to 2.0 — Slightly Overvalued: You're paying a premium above the pace of growth. This can still make sense for high-quality, dependable businesses that the market is willing to pay extra for because of lower risk or a strong competitive position.

2.0 to 3.0 — Overvalued: The share price has run ahead of the growth forecast. Before assuming the stock is simply too expensive, it's worth checking whether the market is pricing in faster growth than the estimate you used — sometimes the market knows something the growth estimate doesn't.

Above 3.0 — Highly Overvalued: A PEG this high almost always means one of three things — the stock is priced for near-perfect execution, the growth estimate being used is too low, or the market has become detached from the fundamentals. Any of the three deserves a closer look before investing.

PEG Ratio vs. P/E Ratio: Why Growth Changes Everything

The P/E ratio and the PEG ratio answer two different questions, and mixing them up is one of the most common mistakes new investors make.

P/E Ratio asks: 'How much am I paying today for $1 of current earnings?' It's calculated as Share Price ÷ Earnings Per Share, and it says nothing about the future.

PEG Ratio asks: 'How much am I paying for $1 of earnings, adjusted for how fast those earnings are growing?' It takes the P/E ratio and divides it by the growth rate, turning a static snapshot into a growth-adjusted one.

Here's why that matters in practice: a slow-growing utility company might trade at a modest P/E of 15, which looks cheap on the surface. But if its earnings are only growing 2% a year, its PEG ratio is 15 ÷ 2 = 7.5 — extremely expensive relative to growth. Meanwhile, a fast-growing software company might trade at a P/E of 40, which looks expensive at first glance. But if earnings are growing 35% a year, the PEG ratio is 40 ÷ 35 = 1.14 — actually a reasonable price. The PEG ratio flips the story that the P/E ratio alone would have told you.

Trailing PEG vs. Forward PEG: Which Should You Use?

There are two common versions of the PEG ratio, and they can give noticeably different answers.

Trailing PEG uses the company's historical earnings growth rate — typically the growth over the past 1 to 5 years — paired with the current or trailing P/E ratio. It's backward-looking and reflects what the company has actually delivered.

Forward PEG uses analyst estimates for future earnings growth, usually a 1-to-3-year forecast, paired with either the current P/E or a forward P/E based on expected future earnings. It's forward-looking and reflects what the market currently expects.

Neither version is automatically 'correct'. Trailing PEG can be misleading if a company's growth is slowing down or speeding up, since it assumes the past will repeat. Forward PEG depends entirely on analyst estimates being accurate, and estimates are frequently revised. Many experienced investors calculate both and compare them — a big gap between the trailing and forward PEG often signals that growth expectations are changing quickly, which is worth investigating further.

The Limitations of the PEG Ratio Every Investor Should Know

The PEG ratio is a useful shortcut, not a perfect valuation model, and it has real limitations worth understanding before you rely on it.

It assumes growth is steady. The formula treats growth as a single flat number, but real companies rarely grow at a perfectly consistent rate every year. A company growing 30% this year and 5% next year has a very different risk profile than one growing a steady 15% both years, even if the average works out the same.

It's only as good as the growth estimate. Since the growth rate sits in the denominator, a small change in the estimate can swing the PEG ratio dramatically. An overly optimistic growth forecast will make a stock look artificially cheap, and an overly conservative one will make it look artificially expensive. Always sanity-check the growth number against the company's actual history and industry conditions.

It doesn't work well for low-growth or negative-growth companies. If a company's earnings are shrinking or barely growing, the PEG ratio becomes unreliable or meaningless — dividing by a very small or negative number produces distorted, sometimes nonsensical results. The PEG ratio is best suited to genuine growth companies, not mature, slow-growing, or cyclical businesses.

It ignores debt, cash flow, and balance sheet risk. Two companies with identical PEG ratios can carry very different levels of financial risk. A company loaded with debt deserves a lower PEG ratio than a debt-free company with the same growth rate, but the formula doesn't account for that on its own.

It doesn't account for dividends. A slower-growing company that pays a meaningful dividend might still deliver a strong total return that the PEG ratio understates, since the formula only looks at earnings growth, not the income an investor receives along the way.

A Real-World Example: Comparing Two Stocks with the PEG Ratio

Imagine you're comparing two companies. Company A trades at a P/E ratio of 30 and is expected to grow earnings 25% a year. Company B trades at a lower P/E of 18 but is only expected to grow earnings 8% a year.

On P/E alone, Company B looks like the cheaper buy. But work out the PEG ratio and the picture changes: Company A's PEG is 30 ÷ 25 = 1.2. Company B's PEG is 18 ÷ 8 = 2.25. Once growth is factored in, Company A — the one with the higher P/E — is actually the better-priced stock relative to its growth prospects. This is the exact kind of mismatch the PEG ratio is designed to catch, and it's why relying on the P/E ratio by itself can lead an investor to the wrong conclusion.

How to Find the Numbers You Need for This Calculator

P/E Ratio: Most finance websites and brokerage platforms display the current P/E ratio directly on a stock's summary page. This calculator's built-in stock lookup will also pull it in automatically for supported tickers.

Earnings Per Share (EPS): Found on the company's most recent quarterly or annual earnings report, or on the same finance websites that list the P/E ratio. Trailing twelve-month (TTM) EPS is the most commonly used figure.

EPS Growth Rate: For a forward-looking PEG, use the analyst consensus estimate for 1-to-3-year forward earnings growth, usually listed under 'analyst estimates' or 'growth estimates' on a stock research page. For a trailing PEG, calculate the annualized growth rate of EPS over the past 3 to 5 years using the company's historical earnings reports.

Using PEG Ratio Alongside Other Valuation Tools

No single ratio should ever be the only factor in an investment decision, and the PEG ratio is no exception. It works best as one piece of a bigger picture.

Combine it with the Price-to-Earnings ratio to understand the raw valuation before adjusting for growth. Pair it with the Dividend Yield Calculator if you're evaluating a company that also pays income to shareholders, since the PEG ratio ignores dividends entirely. Use the DuPont Analysis Calculator to understand the quality of the earnings behind the growth number — fast growth driven by rising debt is very different from fast growth driven by genuine operational improvement. And for companies where a discounted cash flow approach makes more sense, the Dividend Discount Model Calculator offers a different lens on intrinsic value.

The strongest investment decisions usually come from triangulating several of these tools together, rather than leaning on any single number in isolation.

Conclusion: Let Growth Do the Talking

The P/E ratio tells you what you're paying today. The PEG ratio tells you whether that price actually makes sense once you factor in tomorrow. Use this calculator to quickly test whether a stock's valuation lines up with its growth story, compare it against typical sector levels, and work out exactly how much growth a company needs to deliver to justify its current price.

Just remember that the PEG ratio is only as trustworthy as the growth rate you feed into it. Take the time to use a realistic, well-sourced growth estimate, cross-check the result with other valuation tools, and you'll get far more value out of this metric than treating it as a single magic number.