The P/E ratio (price-to-earnings ratio) is one of the most widely used stock valuation metrics in fundamental analysis. A P/E ratio calculator helps investors quickly determine whether a stock is cheap, fairly priced, or expensive relative to its earnings.
How to Use This Calculator
- Enter the current share price of the stock.
- Enter the earnings per share (EPS) — use trailing twelve months (TTM) for historical P/E or next year's estimate for forward P/E.
- Optionally enter a benchmark P/E to estimate fair value.
- Click Calculate to see P/E ratio and implied fair value.
What This Calculator Measures
- P/E ratio — How many dollars investors pay per dollar of earnings.
- Trailing P/E — Uses actual reported earnings over the past 12 months.
- Forward P/E — Uses analyst estimates for next year's earnings.
- Fair value estimate — Share price implied by applying a target P/E to current or projected EPS.
Formula or Logic
P/E Ratio = Current Share Price ÷ Earnings Per Share (EPS)
Fair Value = EPS × Target P/E
If the fair value is above the current price, the stock may be undervalued at that earnings multiple.
Example Calculations
Example 1: Stock price = $150, EPS = $6.00. P/E = 25. At an industry average P/E of 20, fair value = $120 — suggesting the stock is trading at a premium.
Example 2: Stock price = $80, forward EPS estimate = $5.50. Forward P/E = 14.5. If the sector average forward P/E is 18, implied fair value = $99.
Understanding Your Results
The S&P 500 has historically traded at a P/E of 15–25. High-growth sectors like technology often command higher multiples (30–50+). A low P/E could signal value or a deteriorating business — always investigate why.
Common Mistakes to Avoid
- Comparing P/E ratios across different industries (tech vs. utilities are not comparable).
- Using P/E alone without looking at debt levels, growth rate, and profitability trends.
- Not adjusting for one-time items that inflate or deflate reported EPS.
- Overlooking that P/E is backward-looking unless you use forward estimates.