How the Price to Earnings Ratio Calculator works
The price-to-earnings (P/E) ratio is one of the most widely used valuation metrics in equity investing. It compares what a share currently costs to how much profit the company earns per share, giving a quick sense of how expensive a stock is relative to its current earnings.
The core formula
P/E Ratio = Share Price ÷ Earnings Per Share (EPS)
A trailing P/E uses EPS from the last twelve months of actual, reported results. A forward P/E instead uses an analyst's projected EPS for the next twelve months. This calculator treats whatever EPS figure you enter as the basis for the ratio — label it clearly as trailing or forward when you record the result.
Worked example
A stock trading at $150 per share with trailing EPS of $6.00 has a P/E of $150 ÷ $6.00 = 25.0×. That means investors are paying $25 for every $1 of the company's annual earnings. Whether 25× is "cheap" or "expensive" depends entirely on the comparison point — the company's own history, its growth rate, and the P/E of similar companies in the same industry.
The PEG ratio: adjusting for growth
PEG = P/E ÷ Expected EPS Growth Rate (%)
A high P/E is not automatically a red flag if earnings are growing quickly, and a low P/E is not automatically a bargain if earnings are shrinking. The PEG ratio divides the P/E by the expected annual EPS growth rate to normalize for that difference. Using the example above, a P/E of 25× with 10% expected growth gives a PEG of 25 ÷ 10 = 2.5. Many investors treat a PEG near 1.0 as a rough reference point for "growth-adjusted fair value," though this is a heuristic, not a formal valuation rule, and it breaks down for very low or negative growth rates.
Earnings yield
Earnings Yield = (EPS ÷ Share Price) × 100
Earnings yield is simply the reciprocal of the P/E ratio expressed as a percentage. A P/E of 25× corresponds to an earnings yield of 4%. Restating the ratio this way makes it easier to compare a stock's earnings-based return against bond yields or other fixed-income benchmarks that are already quoted as percentages.
Why EPS must be positive
Dividing by a zero or negative EPS produces a number that does not represent a real valuation multiple, so this calculator requires EPS greater than zero. Companies with negative earnings are typically valued using other metrics, such as price-to-sales or price-to-book, until profitability is established.
Limits of the P/E ratio
P/E ratios vary widely by industry, capital structure, and accounting treatment, so comparing a P/E across unrelated sectors is rarely meaningful — this calculator's industry-average comparison is only useful when the comparison figure genuinely reflects similar companies. P/E also says nothing about debt levels, cash flow quality, or one-time accounting items that can distort reported earnings. This tool performs the arithmetic only; it is not investment advice and does not evaluate any individual security.