มูลค่าตลาดของ Apple ที่ 4.3 ล้านล้านดอลลาร์หมายความว่าอย่างไร? คอร์สรู้ทันการประเมินมูลค่าหุ้นที่แม้แต่มือใหม่ก็เข้าใจ

In the previous report, we used Apple Inc. as an example to learn how to read an earnings report. We learned that Apple's earnings per share were $2.01, with a quarterly operating cash flow of $28.7 billion, surpassing analyst expectations on all key metrics. Now, a natural question follows: Knowing all this, is Apple's stock cheap or expensive? More broadly—how do investors truly determine the actual value of a stock?

Key data used in this report: Apple's stock price around $293 to $297 · Market cap $4.32 trillion · Trailing P/E ratio 35.83 · Forward P/E ratio 32.60 · PEG ratio 1.26 · Price-to-sales ratio 9.76 · Free cash flow over the past twelve months $129.1 billion · Dividend yield 0.35%

Section 1 – Why Valuation is the Most Important Skill in Investing

Almost every novice investor falls into the same trap. Its logic goes like this: find a great company, buy its stock, and wait to make money. This logic seems flawless—great companies make money, money flows to shareholders, and shareholders become wealthy.

The problem is that this logic ignores the most critical variable in investing: the price you pay.

Let's illustrate this with a real historical case. In January 2000, Microsoft was one of the most dominant technology companies in the world—its products were on virtually every computer globally, its profits were substantial, and its competitive moat was incredibly deep. Without a doubt, it was a great company.

Two investors both decided to buy Microsoft stock in early 2000. The first bought at the peak of the dot-com bubble at around $60 per share. The second waited for an opportunity and bought after the bubble burst in 2003 at around $21 per share. They owned the same company and received the same dividends. But the first investor waited over fourteen years just for the stock price to return to what they originally paid. The second investor saw their investment triple in just two years.

The same great company, yet vastly different investment outcomes. The only difference was valuation—the price paid relative to the value received.

This is why understanding valuation is an indispensable fundamental skill in investing. It is the dividing line between true "investing" and pure "gambling." Speculation is buying a great company and hoping the price goes up. Investing is buying at a price where the odds are in your favor—so that even if some of your judgments turn out to be wrong, you can still withstand the outcome.

This report will introduce you to the tools professional investors use to determine whether a stock is cheap, fairly valued, or expensive, and more importantly—how to use these tools to make better investment decisions.

Educational Note: The goal of valuation is not to find the "exactly correct price" for a stock—no formula can achieve that. Its goal is to establish a reasonable valuation range, then compare it with the market's current pricing, thereby understanding the expectations already embedded in the current stock price and judging whether those expectations are realistic, overly optimistic, or overly pessimistic. This is both a mathematical exercise and, more importantly, a training in critical thinking.

Section 2 – The Basics: What is a Stock Actually Worth

Before introducing specific tools and ratios, it helps to understand the theoretical foundation of stock valuation. All valuation frameworks, whether simple or complex, ultimately rest on the same core idea: The value of a stock equals the sum of all future cash flows it will generate for its holder, discounted back to today's value.

This might sound abstract, so let's understand it with a concrete example.

Imagine someone offers you this deal: you pay $100 today and receive $10 every year, forever. Your annual return is 10%. If the seller raises the price to $200 but you still receive $10 annually, your return drops to 5%. If the price rises to $1,000, your return is only 1%.

The price you pay determines your return. This isn't complex mathematics, but a simple yet profound truth that forms the bedrock of the entire financial field.

For stocks, future cash flows are uncertain, not fixed—this is what makes valuation both difficult and interesting. Disagreements between investors are almost always about future cash flows—how large they will be, how fast they will grow, how long they will last—and what interest rate to use to discount those future cash flows back to today's value.

Different valuation tools are simply different ways of answering this fundamental question, each with its own focus and limitations.

Educational Note: "Discounting" refers to the process of converting a future sum of money into its present-day value. Because money in hand today can be invested to earn a return, $100 today is worth more than $100 five years from now. The interest rate used to discount future cash flows is called the "discount rate." The higher the discount rate—for instance, when interest rates rise—the less future cash flows are worth today. This is exactly what the report on rising yields in this series described: why rising Treasury yields put downward pressure on stock valuations.

Section 3 – Price-to-Earnings (P/E) Ratio: The Most Widely Used Metric in Investing

The Price-to-Earnings Ratio (P/E) is the most widely cited valuation metric in financial markets. Every serious investor needs a complete understanding of it—both what it can tell you and, equally important, what it cannot tell you.

What is the P/E Ratio

The P/E ratio is calculated by dividing a stock's current price by the company's earnings per share. If a stock trades at $100 and earns $5 per share annually, its P/E ratio is 20. This means investors pay $20 for every $1 of annual earnings.

There are two common versions of the P/E ratio: the trailing P/E uses actual earnings from the past twelve months; the forward P/E uses analysts' estimates of expected earnings for the next twelve months. The forward P/E is usually more relevant for investment decisions because you are buying the company's future, not its past.

Apple's Current Situation

As of June 2026, Apple's trailing P/E ratio is approximately 35.83, its forward P/E ratio is 32.60, the stock price is around $293 to $297, and its earnings per share over the past twelve months are approximately $8.29.

More critical is the historical comparison: Apple's average P/E ratio over the past ten years is 24.51. The current P/E ratio is roughly 46% higher than this historical average.

What does this tell us? Apple's current valuation is on the high side relative to its own history. Investors are paying a higher price for each dollar of earnings than they have for most of the past period. This doesn't necessarily mean the stock is expensive—it could mean the market expects Apple's earnings to grow faster than in the past. But it certainly means the current price embeds high expectations that need to be fulfilled.

What the P/E Ratio Cannot Tell You

The P/E ratio has three important limitations that every investor must understand.

First, it does not account for growth rate. A company growing earnings by 30% annually should command a higher P/E ratio than one growing at 5% annually—even if all else is equal. A P/E of 35 could be cheap for a high-growth company but quite expensive for a slow-growth one. Therefore, the P/E ratio should never be used in isolation.

Second, it can be distorted by one-time items. If a company sells a business unit and books a large one-time gain, its earnings per share will temporarily spike, making the P/E ratio look artificially low. Conversely, the opposite happens if it writes down an asset. When reading financial reports, always check whether the earnings figure in the denominator truly reflects the underlying business performance.

Third, P/E ratios across different industries are not directly comparable. A bank trading at a P/E of 10 is not necessarily cheaper than a software company trading at a P/E of 30. Different industries have structural differences in growth rates, capital requirements, and profit margins, which make different valuation levels reasonable. Comparing P/E ratios is only truly meaningful within the same industry or against a company's own historical levels.

Educational Note: When investors say a stock is trading at "X times earnings," they are quoting the P/E ratio. "Apple is trading at 36 times earnings" means investors are paying $36 for every $1 of profit Apple generates annually. The higher this number, the more optimistic the market is about the company's future growth; the lower it is, the more conservative the expectations—or the more pessimistic the market is about the company's prospects.

Section 4 – The PEG Ratio: Incorporating Growth Rate into Valuation

Precisely because the P/E ratio ignores growth, investors developed the PEG ratio—Price/Earnings to Growth ratio—creating a more complete valuation perspective. The PEG ratio is calculated by dividing the P/E ratio by the expected earnings growth rate, yielding a growth-adjusted valuation metric.

What is the PEG Ratio

If a company has a P/E ratio of 30 and its earnings are growing at 30% annually, its PEG ratio is 1.0. If another company also has a P/E of 30 but its earnings are only growing at 10%, its PEG ratio is 3.0. After adjusting for growth, the first company is clearly cheaper—despite having the same P/E ratio.

Legendary investor Peter Lynch proposed a widely adopted rule of thumb: A PEG ratio of 1.0 represents fair value—you are paying a price roughly equivalent to the company's growth rate. Below 1.0 suggests potential undervaluation; above 1.0 suggests the stock price may already reflect expectations higher than the current growth rate.

Apple's Current Situation

As of June 16, 2026, Apple's PEG ratio is 1.26, based on a P/E ratio of 36.1 and earnings per share growth of 28.7%.

A PEG of 1.26 is slightly above the 1.0 fair value benchmark, but it presents a much milder picture compared to the raw P/E of 36. It tells us: Yes, Apple is not cheap, but the strong earnings growth of nearly 30% provides substantial support for the higher valuation multiple. The PEG ratio transforms "Apple is trading at 36 times earnings" into a more meaningful statement: "Apple is trading at a 1.26 times growth premium"—a distinctly different and much more moderate picture.

Limitations of the PEG Ratio

The reliability of the PEG ratio depends entirely on the accuracy of the growth rate estimates used in the calculation. If analysts' consensus expectations for earnings growth are overly optimistic—which happens frequently—the PEG ratio will appear artificially low, giving a false "cheap" signal. Apple's 28.7% earnings per share growth reflects an exceptionally strong period. Whether this growth rate can be sustained over the next twelve months is the core uncertainty.

Educational Note: Peter Lynch was the legendary manager of the Fidelity Magellan Fund, achieving an annualized return of approximately 29% during his tenure. He popularized the PEG ratio as a tool for finding growth stocks at a reasonable price. His core philosophy was: You are not just paying for current earnings; you are paying for future earnings growth. The ratio of price to growth is the key to determining whether you are paying a fair price. His book "One Up on Wall Street" remains one of the most accessible introductions to stock investing.

Section 5 – Price-to-Sales (P/S) Ratio: Valuing by Revenue

The Price-to-Sales ratio (P/S) divides a company's market capitalization by its total annual revenue, telling you the price investors pay for every $1 of sales the company generates.

Why the P/S Ratio Matters

The P/S ratio is particularly useful in two situations: First, when a company is not yet profitable or its earnings are temporarily suppressed, the P/E ratio cannot be calculated, but the P/S ratio still provides a reference. Second, when comparing different companies within the same industry where there are significant differences in profit margins, the P/S ratio allows for a fairer cross-comparison.

The P/S ratio has a structural advantage over the P/E ratio: Revenue is harder to manipulate through accounting practices than earnings. Companies can make various decisions regarding depreciation, amortization, inventory valuation, and expense timing that affect reported profits, but these decisions usually do not affect revenue. Revenue is the most straightforward and least easily manipulated number on the income statement.

Apple's Current Situation

As of June 2026, Apple's P/S ratio is 9.76, based on a stock price of approximately $297 and a market cap of $4.32 trillion.

A P/S ratio of 9.76 means investors are paying about $9.76 for every $1 of Apple's annual revenue. In absolute terms, this is quite high—most profitable companies have P/S ratios between 1 and 5. However, Apple's exceptionally high gross margins, especially the 76.7% gross margin in its Services business, provide a rationale for its revenue premium over low-margin businesses. A company that retains $0.49 as gross profit for every $1 of revenue earned should logically trade at a higher P/S ratio than a company that retains only $0.20.

The most valuable use of the P/S ratio is horizontal comparison with peers in the same industry and vertical comparison with the same company's historical levels. An expanding P/S ratio means the stock is becoming more expensive relative to its revenue—if gross margins are also improving, this expansion could be justified. If profit margins are declining, it could be a warning sign.

Section 6 – Free Cash Flow Yield: The Professional Investor's Preferred Metric

If you remember only one advanced valuation metric from this report, make it free cash flow yield. It is the most frequently cited metric by sophisticated institutional investors, and for good reason: It is the most direct measure of what you are actually getting from your investment.

What is Free Cash Flow Yield

Free cash flow yield is calculated by dividing a company's annual free cash flow by its market capitalization, or equivalently, dividing free cash flow per share by the stock price. It tells you, for every dollar you invest, what percentage of real cash return you get from the business.

If a company generates $10 billion in free cash flow and has a market cap of $100 billion, its free cash flow yield is 10%. If the market cap rises to $200 billion while free cash flow remains the same, the yield drops to 5%.

Professional investors prefer this metric over the P/E ratio because free cash flow is harder to manipulate than accounting earnings. It represents cash that actually arrives in the company's bank account—cash that can be used to pay dividends, buy back stock, repay debt, or invest in growth.

Apple's Current Situation

Apple's operating cash flow over the past twelve months was $140.2 billion, capital expenditures were $11 billion, resulting in free cash flow of approximately $129.1 billion. Based on a market cap of $4.32 trillion, Apple's free cash flow yield is approximately 3.0%.

At this point, a crucial horizontal comparison is necessary: Apple's business generates free cash flow equivalent to about 3.0% of its market cap. Meanwhile, the current 10-year U.S. Treasury yield is approximately 4.6%. This means risk-free U.S. government bonds currently offer a higher cash income yield than Apple's free cash flow yield, and you take on significantly less risk than holding the stock.

As described in the report on rising yields, this is the core mechanism that puts pressure on high-valuation stocks when interest rates are high. This doesn't mean Apple is necessarily a bad investment—Apple can grow its free cash flow over time, while Treasury rates are fixed. But it clearly highlights: Whether you believe Apple's future growth is sufficient to bridge the gap between its current 3.0% yield and the 4.6% risk-free rate is the most central valuation judgment at this moment.

Educational Note: Free cash flow yield is the inverse of the price-to-free-cash-flow ratio. Apple's price-to-free-cash-flow ratio of about 33 is equivalent to a free cash flow yield of about 3%—both measure the exact same relationship, just from different angles. Investors who prefer the "how much can I earn" framework use the yield; investors who prefer the "how many times am I paying for this cash flow" framework use the multiple. Both lead to the same conclusion.

Section 7 – EV/EBITDA: A Valuation Metric from a M&A Perspective

The Enterprise Value to EBITDA ratio (EV/EBITDA) is the most commonly used valuation tool by investment bankers and analysts when comparing companies with different capital structures. It is more complex than the P/E or P/S ratio but provides a more comprehensive picture of the valuation of the entire enterprise—not just the equity portion.

What is EV/EBITDA

Enterprise Value (EV) represents the total value of a company to all stakeholders—shareholders and creditors. It is calculated as: market capitalization plus total debt, minus cash. EBITDA stands for Earnings Before Interest, Taxes, Depreciation, and Amortization. It is a rough proxy for a company's ability to generate cash from operations, stripping out the effects of financing decisions and accounting choices.

The core value of EV/EBITDA is that it allows for an "apples-to-apples" comparison between companies with different levels of debt. Two companies may look similar in terms of stock price relative to earnings, but if one has no debt and the other has high debt, the latter is actually more expensive—because a potential acquirer would also need to take on that debt.

Apple's Current Situation

Apple's EV/EBITDA is 27.12. This means investors are paying approximately $27 for every $1 of Apple's EBITDA. Historically, the S&P 500's EV/EBITDA has been around 12 to 15. Apple trading at 27 reflects its quality premium