Understanding the Price to Earnings Ratio (P/E Ratio)

The price to earnings ratio, or P/E ratio, helps you understand if a stock is fairly priced. It compares the stock price to how much profit the company earns.
How It Works
The P/E ratio is calculated by dividing the stock price by the earnings per share (EPS).
P/E = Price per Share ÷ Earnings per Share
If a stock is trading at 50 dollars and the company earns 5 dollars per share, the P/E ratio is 10. That means you are paying 10 dollars for every 1 dollar the company earns each year.
What the P/E Ratio Tells You
- A low P/E (for example, 8 or 10) may suggest the stock is cheap or undervalued
- A high P/E (for example, 30 or 40) may suggest the stock is expensive or investors expect big growth
However, different industries have different average P/E ratios. A tech company like Nvidia might have a P/E of 35, while a bank like Westpac might have a P/E around 12.
Example
Company A has a share price of 20 dollars and earns 2 dollars per share.
Company B has a share price of 40 dollars and earns 1 dollar per share.
- Company A: P/E = 20 ÷ 2 = 10
- Company B: P/E = 40 ÷ 1 = 40
Company A is cheaper in terms of earnings. But Company B might be growing faster, which explains the higher P/E.
Key Takeaways
- The P/E ratio compares stock price to company earnings
- A lower P/E may signal better value, but context matters
- Use the P/E ratio to compare companies in the same industry
- It is a useful starting point, not a complete answer

