Valuation
What is a good P/E ratio?
A plain-English explanation of P/E ratios, why valuation matters, and how to think about price versus profit.
A P/E ratio is one of the quickest ways to ask a simple question:
Am I paying a sensible price for this company's profits?
But the number on its own is not enough. A P/E of 8 can be cheap, or it can be a warning sign. A P/E of 30 can be expensive, or it can be reasonable if the business is growing quickly and has years of opportunity ahead.
The useful bit is not memorising the formula. The useful bit is understanding what it is trying to tell you.
The plain-English version
Imagine you could buy the whole company.
If a company is valued by the stock market at £100 million and makes £10 million of profit each year, you are effectively paying 10 years of current profit to own the business.
That is roughly a P/E of 10.
If the same company is valued at £100 million but only makes £1 million of profit, you are paying 100 years of current profit.
At that point you should ask yourself:
Do I really believe this business is going to become much bigger, much more profitable, or much better than it is today?
Company value: £100m Annual profit: £10m Years of profit: 10
Company value: £100m Annual profit: £1m Years of profit: 100
A rough guide
There is no perfect P/E ratio, but this is a useful starting point for UK private investors:
| P/E ratio | Plain-English interpretation |
|---|---|
| Under 8 | Potentially cheap, but check what is wrong |
| 8 to 15 | Often sensible if profits are stable |
| 15 to 25 | Fair if the business is growing |
| 25 to 40 | Expensive unless growth is strong |
| Over 40 | Expectations are very high |
This is only a guide. Different sectors deserve different valuations.
A slow-growing insurer on a P/E of 30 may be difficult to justify.
A high-quality software company on a P/E of 30 might be more reasonable if it is growing profits quickly, has little debt and strong recurring revenue.
Why Robbie Burns-style investors care about valuation
Robbie Burns, author of The Naked Trader, often talks about using common sense before getting lost in complicated ratios.
One useful principle is to compare the value of the whole company with the profit it actually makes.
In simple terms:
How many years of profit would it take to buy the business?
This helps you avoid paying a silly price just because a share has a good story attached to it.
DeepSleepInvest uses this type of thinking inside Sleep Score.
Not because one number can tell you everything, but because valuation matters.
Even a wonderful business can be a poor investment if you pay too much.
Cheap can be dangerous
A low P/E does not automatically mean a bargain.
Sometimes a company is cheap because:
- Profits are about to fall
- Debt is too high
- A dividend cut is coming
- The sector is in decline
- Management has disappointed investors
- The market does not believe current profits are sustainable
This is why valuation should never be used alone.
A company on a P/E of 7 with falling profits and heavy debt may be riskier than a company on a P/E of 18 with rising profits, net cash and a strong record.
Expensive can still work
A high P/E does not automatically mean avoid.
Some companies look expensive for years because they keep growing.
Investors may be willing to pay more for:
- Strong brands
- Recurring revenue
- High margins
- Low debt
- Reliable growth
- High return on capital
- Trustworthy management
The key question is whether the future growth is realistic.
If a company is on a P/E of 35, the market is already expecting good news.
That means there is less room for disappointment.
The question to ask before buying
Before buying a share, ask:
If I bought the whole company today, how many years of current profit would I be paying for?
Then ask:
Am I comfortable with that?
If the answer is no, you may need a very strong reason to invest.
How DeepSleepInvest treats valuation
DeepSleepInvest does not use valuation as a buy or sell signal on its own.
Instead, valuation is one part of the wider Sleep Score.
A company may still score well if it is expensive but high quality.
A company may score badly if it looks cheap but has serious warning signs.
The aim is not to predict next week's share price.
The aim is to help you understand whether the business looks sensible enough to own without checking it every day.
Final thought
A P/E ratio is not magic.
It is simply a way of asking:
How much am I paying for each pound of profit?
If you remember nothing else, remember this:
The more years of profit you pay upfront, the more future growth you need to justify the price.
That is why valuation matters.