Ask whether stocks or crypto is “better” and you will get an argument disguised as an answer. Ask how the two assets divide up a portfolio and you are finally asking an investor’s question. This guide looks at crypto and stocks the way a portfolio manager would: not through headlines or ideology, but through returns per unit of risk, correlation between the two assets, behaviour in different economic environments, and the practical sizes of allocation that make sense. Throughout, keep in mind that crypto is covered in depth elsewhere on this site, from the basics to the scams and the tax rules; this article exists purely as the comparison. And the comparison has one central, maybe surprising conclusion: on a risk-adjusted basis, the two have historically been far closer than the headline numbers suggest.
Risk-adjusted returns: not what the headlines say
Raw returns flatter crypto. When you strip the risk out of the numbers, the picture changes. The table below summarises the comparison commonly quoted for the decade to 2025 — treat every figure as a rough, historical estimate rather than a projection:
| Measure | S&P 500 | Bitcoin |
|---|---|---|
| Annualised return (2015-2025) | ~12% | ~50% |
| Annual volatility | ~16% | ~70% |
| Worst calendar-year drawdown | -18% | -64% |
| Approximate Sharpe ratio | ~0.6-0.7 | ~0.6-0.7 |
Two things stand out. First, Bitcoin’s headline return roughly scales with its extra volatility — the ~50% annualised return and the ~70% volatility are two sides of the same coin. Second, and far more important, once you adjust for that risk — the Sharpe ratio measures how much return you get for each unit of volatility you endure — the two assets land in the same bracket. Crypto’s spectacular returns are a reward for spectacular risk, not an anomaly that beats the system. Any honest allocation discussion has to start from that fact, because it changes the question from “which will win?” to “how much of this volatility can my plan absorb?”
Correlation: the diversification case
Correlation is the technical term for how closely two assets move together, and it is the entire basis on which diversification works. Diversification only helps when the things you own do not fall at the same time; if everything in your portfolio halves together, spreading your bets bought you nothing. Measured against the S&P 500, Bitcoin’s correlation has been unstable across recent cycles: roughly 0.2 (low) in 2015-2019, roughly 0.6-0.8 (high) in 2020-2022, and moderate at around 0.4-0.5 in 2023-2025.
That pattern is the problem with the “diversifier” label that crypto fans sometimes attach. In 2020-2022 crypto traded like a high-beta technology stock — superb in bull markets, useless as protection in sell-offs. And in stress events the correlation has spiked toward 1: in the March 2020 liquidity crunch the two assets fell together, almost in lockstep. Expect similar behaviour in the next crisis, because correlation rises precisely in the risk-off environments where an investor most wants cover. A small allocation may still add something to a portfolio; just do not call a small crypto holding a hedge. It is participation in a risk-on asset, not insurance.
Behaviour in different environments
Thinking about macro environments makes the picture concrete. In periods of rate cuts and abundant liquidity, stocks are strong and crypto is arguably strongest of all, because it behaves as a speculative beta — a magnified version of the riskiest equity exposure you could own. In high-inflation, rising-rate periods, stocks tend to be weak to moderate and crypto has historically been mixed; the “digital gold” narrative has not held up in practice. In a recession or broader risk-off mood, stocks fall and crypto has tended to fall harder. A strong dollar tends to weigh on crypto because it is priced in dollars even if you buy it with pounds, while its effect on stocks is more mixed. And regulatory headlines — which barely dent a diversified equity portfolio — can move crypto prices sharply on sentiment alone. All of this points one way: crypto behaves like an aggressive growth asset, not a safe haven, and it should be sized accordingly.
Portfolio construction: how much crypto
Putting numbers on this is the practical step. The illustration below considers a reference portfolio of 60% stocks, 30% bonds and 10% cash, and how adding different crypto slices might affect it. The figures are indicative approximations, not precise forecasts, but they capture the shape of the trade-off:
| Crypto allocation | Approx. return impact | Approx. max-drawdown impact |
|---|---|---|
| 0% | Baseline | Baseline |
| 1-2% | +0.1 to +0.3% | Negligible |
| 2-5% | +0.2 to +0.8% | Slightly deeper |
| 5-10% | +0.5 to +1.5% | Noticeably deeper |
| 10%+ | Tail risk dominates | Portfolio defined by crypto |
The pattern is the whole argument. The extra return from a small allocation is meaningful but modest — fractions of a percentage point — and the extra drawdown from a small allocation is equally modest. That is precisely the point. A slice in the 2-5% range buys some upside participation without letting one asset’s -70% year define your results. A 5% slice cannot break you; a 20% slice turns every crypto crash into a portfolio-wide crisis. If 2-5% feels too small, that is usually a sign you are sizing on hope rather than on the drawdowns in the table above — the honest way to size is to look at what you could lose, not what you hope to gain.
Practical allocation guidance
For different investor profiles the sensible starting points differ. A new investor still building the basics is best served by 0-1%, and only once the stock core exists. An accumulator with a high risk tolerance might use 2-5%, bought by monthly averaging into a separate wallet. An established, balanced investor might run 2-3%, rebalanced annually within a band. Someone near retirement is generally best at 0%, focusing on income-producing assets. And a speculative trader will do whatever their own strategy dictates — but that is trading, not investing, and should be counted and capitalised separately.
How you implement matters as much as how much: build the stock and bond core first, using global index funds inside an ISA or SIPP, so the crypto slice is genuinely the satellite and not the payload. Size the crypto slice to a number you could lose completely, because that is a real scenario for the asset class. Buy via regular monthly averaging rather than a lump sum, so you are never paying a peak price for everything at once. Rebalance the core normally and let the crypto slice drift within its band of, say, 2-5%. And only ever sell crypto when it breaks out of that band — never react to market timing impulses within it.
Bottom line
For an investor, stocks and crypto are not rivals competing for a single slot; they are different risk buckets inside one portfolio. Risk-adjusted, crypto has historically rewarded its volatility rather than beaten it — the extraordinary returns come with extraordinary swings. Correlation data says to treat crypto as a high-beta growth asset, not a hedge, because it tends to fall with stocks precisely when you want protection. The practical allocation is therefore small: a few per cent, bought by monthly averaging, rebalanced with bands, and sized to a total loss you could genuinely absorb. Build the stock and bond core first, treat any crypto as the satellite it should be, and — for a broader education on the asset class itself — the crypto sections of this site go far deeper than this comparison does. This article is education, not financial advice; the right size for your own portfolio depends on your circumstances.