Entry P/E Ratio
Calculates the maximum P/E ratio to pay today so that compounding earnings growth, sold at an assumed exit P/E, delivers the required rate of return — with an optional margin of safety discount.
When to use: Use when you have a view on exit P/E, expected earnings growth, holding period, and required return. Leave MOS blank for the unadjusted maximum or enter a decimal (e.g. 0.25) to build in a valuation cushion.
Formula
Variables
| Symbol | Name | Description | Unit |
|---|---|---|---|
| EntryPE | Entry P/E Ratio | Maximum P/E multiple to pay today for the target return | integer |
| ExitPE | Exit P/E Ratio | Expected price-to-earnings multiple at exit | integer |
| g | Earnings Growth Rate | Expected annual EPS growth as a decimal | % |
| r | Required Return | Annual required rate of return as a decimal | % |
| n | Holding Period | Years held before exit | years |
| MOS | Margin of Safety | Discount applied for valuation cushion as a decimal | % |
Real-Life Examples
Example 1: Quality Compounder (no MOS)
A high-quality business is expected to grow EPS at 12% for 10 years and trade at a 20× P/E at exit. You require a 10% return and apply no margin of safety.
Given
Step-by-Step
You can pay up to 23.95× earnings today and still earn 10% if the company grows at 12% and exits at a 20× multiple.
Example 2: Compounder with 25% MOS
Same setup as above (Exit P/E 20×, 12% growth, 10% return, 10 years), but you demand a 25% margin of safety.
Given
Step-by-Step
Buy at 18× or below — 25% lower than what the unadjusted model justifies, protecting against optimistic inputs.
Frequently Asked Questions
The entry P/E ratio is the highest price-to-earnings multiple you can pay today and still hit your required return, given assumptions about earnings growth, holding period, and exit P/E. It rearranges a future-value equation into a multiple you can compare to current market prices.
Higher expected earnings growth increases the future value of the business, which lets you pay a higher P/E today and still hit your hurdle rate. The relationship is exponential — small differences in growth rate compound into large differences in justified entry multiple over long holding periods.
If the market price implies a P/E below your calculated entry P/E, the stock may be undervalued relative to your assumptions. If the market P/E is above your entry P/E, the implied return falls below your hurdle rate — either lower your required return, raise your growth assumption, or pass.
No — leave MOS blank (or set it to 0) for the unadjusted maximum entry P/E. Enter a decimal between 0 and 1 to discount that multiple by the chosen percentage.