Bruno Koba
How Often Should You Rebalance Your 401(k)? A Clear Answer for Young Investors
Here's a scenario that plays out a lot: you started your first real job, sat through the HR onboarding session, picked some funds that sounded reasonable, and moved on. That was two, maybe three years ago. You've checked the balance a few times. Things look... fine? Probably fine. You're not sure.
The thing you almost certainly haven't done is rebalance. And if you're being honest, you're not entirely sure what that means or how often you're supposed to do it.
The Short Answer
Once a year. That's the answer Vanguard, Fidelity, and most independent research agree on. More frequent rebalancing generally doesn't improve returns and creates more opportunity for mistakes.
A slightly better answer: once a year, OR any time your target allocation drifts by more than 5 percentage points, whichever comes first.
What Rebalancing Actually Means
When you picked your 401(k) investments, you probably chose a mix like 80% stocks and 20% bonds. That's your target allocation, matched to your risk tolerance and timeline.
Over time, different assets grow at different rates. In a strong market, stocks grow faster than bonds. After a couple of years without intervention, that 80/20 portfolio might now be 88/12, meaning you're carrying more risk than you signed up for.
Rebalancing is the act of selling what's grown and buying what's lagged, to return to your target allocation. The counterintuitive result: rebalancing forces you to sell high and buy low.
Why Annual Is the Sweet Spot
Vanguard research finds that for most investors, annual rebalancing produces results statistically indistinguishable from quarterly or monthly, while generating fewer transaction costs.1
Momentum has time to play out. Monthly rebalancing cuts winners too early.
Less opportunity for emotional mistakes. The more often you act, the more chances you have to sell into panic or chase a rally.
It's simple. Pick a date. Rebalance. Done for the year.
Time-Based vs Threshold-Based
Time-based: rebalance on a calendar schedule, regardless of drift.
Threshold-based: rebalance only when your allocation drifts more than 5 points.
The hybrid most pros use: check once a year, rebalance if any allocation is off by more than 5 percentage points, otherwise leave it alone.
When to Rebalance Off-Cycle
Major market moves. Stocks drop 25%+ or rally 30%+ in a short window? A quick mid-year check makes sense.
Change in risk tolerance or timeline. Got married, had a kid, bought a house, got closer to retirement? Your target allocation may need to change.
Major contribution or withdrawal. Rolling over an old 401(k) is a good moment to land in your target mix.
The Easiest Way: Automatic Rebalancing
Most 401(k) plans offer automatic rebalancing. Log in to your plan, find the setting, and choose a frequency. For most people, turn it on, set it to annual, forget about it.
The caveat: automatic rebalancing only works within the 401(k) itself. If you have multiple accounts, you'll need to coordinate manually.
Target Date Funds Rebalance for You
If you're in a target date fund, the fund itself rebalances internally and gradually shifts from stock-heavy to bond-heavy as the target date approaches. You don't need to do anything.
The tradeoffs are slightly higher fees (typically 0.10% to 0.25%) and less control over the glide path.
Why Rebalancing Matters More Than You Think
Rebalancing isn't about maximizing returns. It's about managing risk.
Say you set up an 80/20 portfolio at 25. Twelve years in, without rebalancing, you might be at 92/8. A major drawdown hits. Your portfolio drops 45% instead of 35%. You panic, sell at the bottom, and lock in a loss that takes a decade to recover.
Rebalancing ensures your portfolio doesn't quietly drift into a risk profile you can't handle emotionally. Once it's rebalanced, the more important ongoing question is whether your overall allocation still matches your goals.
The Bottom Line
Rebalance your 401(k) once a year. Use a 5-percentage-point drift threshold as a trigger. Or turn on automatic rebalancing and never think about it again.
What you should not do: rebalance monthly, rebalance reactively after market moves, or never rebalance at all.
See also: why time in the market beats timing the market and the 10-step financial plan guide.
FAQ
How often should I rebalance my 401(k)?
Annually is the right cadence for most investors. A 5-percentage-point drift threshold is a reasonable additional trigger.
Is it bad to rebalance too often?
In a 401(k), there are no tax consequences, but over-rebalancing cuts winners short. Monthly is overkill.
Should I rebalance during a recession?
Yes, if your allocation has drifted from target. A crash pushes stock allocations down, meaning rebalancing during a downturn means buying low.
Do target date funds rebalance automatically?
Yes. They handle internal rebalancing and gradually shift from equities to bonds as the target date approaches.
What's the difference between rebalancing and reallocating?
Rebalancing returns your portfolio to its existing target. Reallocating changes the target itself (e.g., 80/20 to 70/30 because you're closer to retirement).
References
Best Practices for Portfolio Rebalancing — Vanguard
Portfolio Rebalancing: When and How — Fidelity
401(k) Plans — IRS
This article is not personalized financial advice. For personalized guidance tailored to your situation, Astor is an SEC-registered investment advisor that provides personalized recommendations.