Crypto in a Retirement Portfolio: What a Long-Term Simulation Actually Shows
6 min read
Loading...
6 min read
Bitcoin peaked near $126,198 in October 2025. By August 6, 2026, it was trading at $64,509.85, down about 49% from that peak. If you are 25 years from retirement and wondering whether a small crypto slice belongs in that portfolio, a swing like that is exactly the kind of question a single price chart cannot answer. You need to know what happens over decades, not over one bad month.
This post walks through a real backtest that added Bitcoin to a traditional 60/40 portfolio (60% stocks, 40% bonds) and measured what changed. It also explains why "running the numbers" for something this volatile means looking at a range of outcomes, not one confident answer.
Fidelity Digital Assets ran a backtest for its 2026 report "Getting Off Zero," testing a standard 60/40 portfolio against the same portfolio with a small slice of Bitcoin added, from January 1, 2018 (shortly after Bitcoin futures started trading) through March 31, 2024, a period of roughly six years that included two full bitcoin bull-and-crash cycles.
The result: adding just a 1% Bitcoin allocation to the 60/40 portfolio raised the portfolio's compounded return by roughly 30% over that test window, and improved its Sharpe ratio by roughly 20%.
Sharpe ratio is a simple idea with a technical name. It measures how much return a portfolio earned for each unit of risk it took on. A higher Sharpe ratio means you got paid more for the risk you carried, not just a bigger number on the return line.
The surprising part is what happened to drawdown, the size of the portfolio's worst peak-to-trough loss during the period. Even with Bitcoin's history of brutal crashes, the 1% allocation increased the 60/40 portfolio's maximum drawdown by only about 0.5 percentage points. A small slice of a very volatile asset barely moved the portfolio's worst-case loss, because it started from such a tiny base.
Here is the part that matters just as much as the upside. In the same Fidelity backtest, replacing 1% of a 60/40 portfolio with Bitcoin contributed roughly 2.7% of the total portfolio's volatility. Push that allocation up to 5%, and Bitcoin's contribution to total portfolio volatility jumps to roughly 17.8%. A five-times bigger allocation produced a bit more than six times the volatility contribution.
Volatility, in plain terms, is how much an investment's value bounces around. It is not the same thing as losing money permanently, but it is what makes an investment hard to hold through a bad year without panicking.
Bitcoin's own volatility is a different order of magnitude from stocks. Measured from 2015 onward, Bitcoin's annualized volatility runs around 54.4%, versus about 13.0% for the S&P 500, roughly four times higher, according to Bloomberg data analyzed by Winthrop Wealth. Looking at Bitcoin's full 10-year average instead, its annualized volatility comes in around 46.31%, still close to five times the S&P 500's 9.64% over the same stretch, per Forbes and Spark Money's tracking. And Bitcoin has done this while surviving multiple drawdowns in the 40% to 70% range along the way, the same kind of drop it is going through again right now, down 49% from its October 2025 peak.
That is why the position sizing matters more than the decision to include Bitcoin at all. A 1% slice barely moves your portfolio's worst case. A 5% slice moves it a lot.
Suppose a 60/40 portfolio, with no crypto, compounded from Rp100,000,000 to Rp150,000,000 over a roughly six-year stretch, matching the length of the Fidelity test window above. This Rp100 juta starting point is a round hypothetical, not a real historical result, used only to apply the study's real percentage.
Based on Fidelity's finding that a 1% Bitcoin allocation raised compounded returns by roughly 30% over that same length of test period, the version of that portfolio with a 1% Bitcoin slice would have compounded to roughly Rp195,000,000 instead of Rp150,000,000, a genuinely large difference from a genuinely small allocation.
That gap is the whole argument for a small crypto sleeve in a long-horizon portfolio. It is also exactly why the position has to stay small: the same math that produced that upside came from an asset that can lose half its value in under a year, as it just did.
A single backtest tells you what happened in one specific stretch of history. It does not tell you what could happen next, because the next 20 or 30 years will not replay 2018 to 2024 in order.
This is what a Monte Carlo simulation is for. Instead of running your portfolio through one historical path, it runs it through thousands of randomized paths built from realistic return and volatility assumptions, then reports the range of outcomes rather than a single number. Retirement planning tools typically summarize that range using percentiles: a 10th percentile result (a genuinely bad run of markets), a 50th percentile result (the typical outcome), and a 90th percentile result (a genuinely good run), a structure described in T. Rowe Price's own explainer on using Monte Carlo analysis for retirement planning.
Add a volatile asset like Bitcoin to that simulation, even in a small amount, and here is the honest version of what happens: the spread between the 10th and 90th percentile outcomes widens. Your best-case outcomes get better. Your worst-case outcomes also get somewhat worse. A single "expected return" number hides that trade-off completely. A range of outcomes does not.
If you are decades from retirement, the data above supports a specific, narrow conclusion: a small crypto allocation, in the low single digits of a portfolio, has historically added more to returns than it added to worst-case losses, in the one long backtest period studied here. It does not support going bigger than that on the strength of the same numbers, since the volatility contribution scales up much faster than the allocation itself.
You do not have to take a backtest's word for what fits your own plan. NetWort's portfolio simulator runs your actual holdings, including any crypto positions, through the same kind of range-of-outcomes analysis described above, so you can see your own 10th, 50th and 90th percentile paths instead of someone else's. If you want to see what a small Bitcoin position specifically has done on its own, Bitcoin's asset page carries its live price and history.
This is related reading, not a next step to take blindly: How much of your portfolio should go into crypto? looks at the sizing question this post assumes, in more depth.