Financial Ratios for Pro Investors Looking for Value

8.6 Key Ratios to Know (P/E, P/B, ROE, etc.): The Investor’s Rulebook

“If you don’t know jewelry, know the jeweler.” — Warren Buffett

Investing is a game of separating the gold from the fool’s gold. Every company presents itself as valuable, but how do we determine if it’s truly worth owning? The answer lies in key financial ratios—the fundamental metrics that reveal whether a business is a compounding machine or a mirage.

Think of these ratios as the investor’s toolkit, much like a physicist uses formulas to describe the universe or a composer uses notes to build a symphony. Each ratio is a lens through which we view profitability, efficiency, and valuation, helping us answer the essential question: “Is this business worth investing in?”

Step 1: Valuation Ratios – What Are You Paying?

Before we buy a company, we must ask: “Am I getting a bargain, or am I overpaying?” These ratios help us measure the price we pay relative to value.

1. Price-to-Earnings Ratio (P/E): The Classic Yardstick

Formula: P/E = Price per Share ÷ Earnings per Share (EPS)
Meaning: How many dollars investors are willing to pay for each dollar of earnings.

Investor’s Rule of Thumb:

A high P/E (above 25-30) suggests a stock is expensive or expected to grow fast.
A low P/E (below 10-15) may signal a bargain or a struggling business.

Example:

Company A trades at $100 per share and earns $5 per share → P/E = 20
Company B trades at $50 per share and earns $10 per share → P/E = 5

Company A is more expensive relative to earnings. But does that mean it’s overvalued? Not necessarily—P/E must be compared to industry peers.

🔎 What Buffett Would Say:
“It’s far better to buy a wonderful company at a fair price than a fair company at a wonderful price.” A high P/E is fine if future growth justifies it.

2. Price-to-Book Ratio (P/B): The Asset Test

Formula: P/B = Price per Share ÷ Book Value per Share
Meaning: How much investors are paying relative to the company’s net assets.

A P/B below 1 means the stock is trading for less than the company’s actual assets—often a sign of deep value investing opportunities.

Example:

A company with a P/B of 0.8 means investors can buy $1 worth of assets for 80 cents.
But if that company is in decline, those assets may not be as valuable as they appear.

🔎 What Graham Would Say:
Benjamin Graham, the father of value investing, loved low P/B stocks because they offered downside protection—you were paying less than the business was worth on paper.

3. Price-to-Sales Ratio (P/S): Revenue-Based Valuation

Formula: P/S = Market Cap ÷ Total Revenue
Meaning: How much investors are paying for each dollar of revenue.

A low P/S can indicate a potential bargain, while a high P/S suggests high expectations for growth.

Example:

If a company has $1 billion in revenue and a market cap of $2 billion, the P/S ratio is 2.
If another company has $500 million in revenue but a market cap of $10 billion, its P/S is 20—much pricier.

🔎 Why It Matters:
P/S is useful for analyzing growth stocks that don’t yet have earnings (like early-stage tech companies). But high P/S stocks are risky if growth slows.

Step 2: Profitability Ratios – How Well Does the Business Generate Money?

A business that isn’t profitable is like a symphony that never resolves—lots of noise but no harmony. These ratios tell us if a company is actually making money.

4. Return on Equity (ROE): The Business Efficiency Test

Formula: ROE = Net Income ÷ Shareholders’ Equity
Meaning: How effectively a company generates profit from shareholder money.

Investor’s Rule of Thumb:

ROE above 15% is strong—indicates a high-quality business.
ROE below 10% suggests weak profitability.

🔎 What Buffett Would Say:
“The best businesses have high returns on equity with little or no debt.” He looks for businesses that compound shareholder money efficiently over time.

5. Return on Assets (ROA): How Well Are Assets Used?

Formula: ROA = Net Income ÷ Total Assets
Meaning: How efficiently a company converts its assets into profit.

ROA is particularly useful when analyzing asset-heavy industries (banks, utilities, real estate).

Investor’s Rule of Thumb:

ROA above 5% is solid.
ROA below 2% may signal inefficiency.

Step 3: Leverage Ratios – Is the Company Carrying Too Much Debt?

Debt is a double-edged sword. Used wisely, it can fuel expansion. Used recklessly, it can sink a company.

6. Debt-to-Equity Ratio (D/E): The Risk Meter

Formula: D/E = Total Debt ÷ Shareholders’ Equity
Meaning: How much debt a company has relative to its equity.

A high D/E ratio means a company is highly leveraged—which increases risk if interest rates rise.

🔎 Investor’s Rule of Thumb:

D/E below 1.0 = Generally safe.
D/E above 2.0 = Potentially risky, depending on industry.

🔎 What Munger Would Say:
“Smart investors avoid unnecessary debt. If you’re smart, you don’t have to borrow. If you’re dumb, you shouldn’t.”

Step 4: Growth Ratios – Is the Company Expanding?

A business that isn’t growing is like a composer who’s lost his inspiration—stagnant and uninspiring.

7. Earnings Growth Rate (EGR): The Expansion Indicator

Formula: EGR = (Current Earnings – Past Earnings) ÷ Past Earnings
Meaning: How fast a company’s earnings are growing over time.

Investor’s Rule of Thumb:

Consistent 10-20% growth is a sign of a strong company.
Erratic or negative growth raises red flags.

Final Takeaways: The Investor’s Rulebook

Valuation Matters – P/E, P/B, and P/S help determine if you’re overpaying or getting a deal.
Profitability Wins Over Time – ROE and ROA separate great businesses from mediocre ones.
Debt Can Be Dangerous – High D/E ratios signal risk, especially in downturns.
Growth Must Be Sustainable – Earnings growth is key, but it must be consistent.

Final Thought: Investing as a Masterpiece, Not a Gamble

A great investor is like a great composer—arranging different elements in perfect balance. The best investments aren’t made on hunches but on sound principles, measured risk, and a deep understanding of value.

Or, as Warren Buffett put it:

“Risk comes from not knowing what you’re doing.”

And now, dear investor, you know what you’re doing.