PEG Ratio: The Metric That Tells You If a 'Cheap' Stock Is Actually Cheap

A low P/E ratio is often read as "this stock is cheap," but that can be genuinely misleading without accounting for growth. The PEG ratio fixes this by adjusting P/E for the company's expected earnings growth rate.

Why P/E alone can mislead

A stock trading at a P/E of 30 might look "expensive" compared to one at a P/E of 10 — but if the first company is growing earnings 30% per year and the second is growing just 2%, the higher P/E stock may actually represent better relative value once growth is factored in. P/E in isolation ignores this entirely.

The formula

PEG = P/E Ratio ÷ Earnings Growth Rate (%)

A PEG around 1.0 is traditionally considered fairly valued — the P/E roughly matches the growth rate. A PEG meaningfully below 1.0 suggests the stock may be undervalued relative to its growth, while a PEG well above 1.0 suggests the market may be pricing in more growth than is likely to materialize.

A worked comparison

Company A: P/E of 25, expected earnings growth of 25% → PEG of 1.0 (fairly valued relative to growth). Company B: P/E of 12, expected earnings growth of 4% → PEG of 3.0 (despite the "cheaper" looking P/E, it's actually more expensive relative to its growth prospects). This is exactly the kind of case where PEG flips the naive "lower P/E is cheaper" intuition.

Limitations worth knowing

PEG depends entirely on the growth rate estimate used — analyst projections can be wrong, and using historical growth instead of forward estimates can give a misleading picture for a company whose growth is accelerating or decelerating. PEG also doesn't account for differences in risk, debt levels, or capital efficiency between companies — it's a useful first filter, not a complete valuation on its own.

Best used alongside other metrics

PEG works well as a quick screening tool to flag stocks worth deeper investigation, but pairing it with other approaches — like a full DCF valuation or an EV/EBITDA comparison against direct peers — gives a much more complete picture than any single ratio alone.

Calculate it for any stock

The free PEG Ratio Calculator shows exactly where a stock falls on the valuation scale relative to its growth rate. For a deeper valuation, the DCF Valuation Calculator estimates intrinsic value directly from projected cash flows.