Reading P/E and P/B — What 'Cheap' Actually Means
- •P/E = how many times earnings the price is
- •P/B = how many times book equity the price is
- •Low usually has a reason — finding it is the work
What the two measure
P/E divides the price by earnings per share. A P/E of 10 can be read as taking ten years to earn back the price if profits hold. P/B divides the price by book value per share, showing how many times the liquidation value the shares trade at.
| Metric | Compared against | Fits |
|---|---|---|
| P/E | Earnings | Steady earners |
| P/B | Book equity | Asset-heavy sectors |
Does low mean cheap?
A low P/E usually has a reason: a declining industry, deteriorating earnings, or regulatory risk. If the market expects profits to fall, today's low multiple is an illusion — halve the earnings and the P/E doubles on its own.
The same applies to a P/B below 1. It means trading under book value, but whether those assets are truly worth their book figure is a separate question. Unsellable inventory or ageing equipment can exist only on paper.
How to compare
- Compare within the same industry — fair multiples differ
- Compare against the company's own historical average
- Account for whether it is growing or mature
- Check whether a one-off gain is flattering the P/E
- For indebted firms, check enterprise-value multiples too
When they do not work
Loss-making companies have no P/E at all — the calculation is meaningless with negative earnings. Asset-light software and service companies make P/B weak too, because their value sits in brands and people that never reach the balance sheet. So the order matters: understand how the business earns before reaching for a single ratio.
Frequently Asked Questions
What P/E is reasonable?
There is no absolute level. Fast-growing sectors trade higher and mature ones lower. Using the sector average and the company's own history as two reference points is more practical.
Should I avoid high-P/E stocks?
A high P/E means the market expects earnings to grow substantially. If that happens, fine — if not, the correction is sharp. The key is seeing how much expectation is already in the price.
What is PEG?
It divides the P/E by the earnings growth rate, adjusting the multiple for growth. Near 1 is read as priced in line with growth. But if the growth estimate is wrong, so is the ratio.
Where can I check these?
Brokerage apps and financial data sites show them per stock. Note whether the figure uses the last four quarters or forecast earnings — the numbers differ, so check the basis.
Does the index-level P/E matter?
It helps gauge where the market sits historically. Timing with it is unreliable, though — elevated valuations often persist for years.