How to Calculate Trailing and Forward P/E Ratios

Start with the earnings basis

The same stock can have several P/E ratios at the same price. The earnings period, dilution basis and accounting adjustments determine which figure you are looking at.

What trailing and forward P/E measure

P/E measures the share price per unit of positive earnings per share. Trailing EPS covers the last 12 months of actual earnings. Forward EPS is an estimate for the next 12 months.

Some providers use a fiscal-year forecast rather than the next 12 months. Verify the period before using their estimate in this calculator.

Reconcile two P/E quotes

Record the quote date, listing, currency unit, reporting period, basic or diluted EPS, and whether the number is reported or adjusted. Recompute with a matched price and denominator, then compare the source definitions.

Price-to-earnings formula

Divide a positive share price by positive earnings per share. Use the same currency units and share basis for both. The result is dimensionless and expressed as a multiple.

P/E = share price ÷ earnings per share

Compare two verified multiples

A share price of 50 and trailing EPS of 2 give 25.00×. At the same price, forward EPS estimated at 4 gives 12.50×. The lower forward multiple comes from the larger estimated denominator.

1. Enter share price 50 and actual trailing EPS 2 to get 25.00×.
2. Change the horizon to forward, which clears EPS but keeps the price.
3. Enter next-12-month estimated EPS 4 to get 12.50×.

Choose matching inputs

Choose the EPS horizon. Enter positive price and signed EPS in matching units. Switching horizon clears EPS so that an actual figure cannot silently become a forecast.

If you derive EPS from a company's report, use the proper weighted-average share count and earnings attributable to common holders. Check the EPS guide before using a reported or adjusted figure.

Interpret zero, losses and small earnings

Zero EPS makes the division undefined. Negative EPS indicates a loss and does not give a meaningful conventional P/E multiple. Very small positive EPS can produce a very large multiple.

A change in P/E can come from price, earnings or both. At a fixed price a lower forward multiple implies a higher supplied earnings estimate, which may change.

P/E, earnings yield and enterprise value

Positive earnings yield reverses the division and is usually shown as a percentage. Enterprise value uses a different capital structure perspective. Comparing companies requires consistent denominators and attention to growth, risk and earnings quality.

Keep the share basis consistent

Match the security, currency unit and share basis. When comparing multiples, use comparable horizons and check whether EPS is basic or diluted and reported or adjusted.

If shares split, use price and EPS on the same adjusted basis. A depositary receipt can represent a fraction or multiple of an underlying share. Compare each price with earnings for the same economic unit.

Input limits and rounding

Each input accepts up to 48 trimmed characters and 12 decimal places, with magnitude no greater than 10^15. Positive multiples from 10^−27 through 10^27 are supported. Display rounds half-even to two decimals and marks positive values that round to zero.

A forecast is supplied by the user. The calculator does not pull analyst estimates or annualise partial periods.

Avoid mixing units and reporting periods

Do not mix pounds with pence, share price with total earnings, or a depositary receipt with unmatched EPS for an underlying share. Avoid substituting a quarter's EPS or silently annualising it.

A 500p price and EPS of £0.20 become 5 ÷ 0.20 = 25× when both are expressed in pounds. Using 500 ÷ 0.20 without conversion would overstate the multiple by 100 times.

Compare inputs across five markets

Use USD for a US-dollar listing, GBP or matching pence for a UK quote, CAD for a Canadian-dollar listing, AUD for an Australian-dollar listing, and INR for an Indian-rupee listing. Check presentation currency independently of exchange venue and match depositary-receipt units where relevant.

ASX describes a 12-month earnings multiple per security. NSE's index methodology aggregates market capitalisation and earnings, so the index value should not be treated as a single-stock calculation.

Educational scope

Educational valuation multiple based on supplied inputs. No automatic forecasts, currency conversion, corporate-action adjustments, target prices or personalized investment advice.

Frequently asked questions

Sources and review

Sources reviewed Nov 9, 2026. Consult current local rules before relying on time-sensitive information.

• Damodaran: valuation definitions
• ASX glossary
• NSE index methodology
• SEC depositary receipt bulletin