Most 401(k) plans give you 20–40 fund choices and zero context. People stare at the list, panic, and either pick whatever "growth" fund sounds confident or leave the contribution sitting in a money market default. Both choices cost money over decades.
This guide gives you a 5-minute decision framework, not a doctorate in modern portfolio theory.
What changed in 2026
- Target-date funds keep getting better. Vanguard, Fidelity, and Schwab series have expense ratios near 0.10–0.15%.
- Brokerage windows are common. Many plans now let you invest in any ETF, not just the curated menu.
- SECURE 2.0 effects. Auto-enrollment is the default for new plans, and Roth options are more widely available.
The 5-minute decision framework
- Look for a target-date fund. If your plan offers one with an expense ratio under 0.20%, you're done.
- If no good TDF, build a 3-fund portfolio. Total US + total international + bonds.
- Match age-appropriate equity allocation. Roughly (110 minus age) % in stocks.
- Check the expense ratio. Anything over 0.50% is a red flag; consider the brokerage window if available.
- Set and forget. Rebalance once a year, not weekly.
1. Target-date funds — best default for most people
A target-date fund (e.g., "2055 Target Retirement") holds a diversified mix of US stocks, international stocks, and bonds, and gradually shifts toward bonds as you approach the target year. Pick the year closest to your planned retirement and stop thinking about it.
The trade-off: not all TDFs are equal. Vanguard, Fidelity Freedom Index, and Schwab series are excellent at 0.08–0.15%. Active TDFs (American Funds, T. Rowe Price active) charge 0.50–0.70% — meaningful drag over decades.
2. The three-fund portfolio — best for DIY
If your plan has good index funds but no acceptable TDF, build it yourself. Common allocation at 35: 60% US total stock (FXAIX, VTSAX), 25% international (VTIAX, FSPSX), 15% bonds (VBTLX, FXNAX). Adjust by age.
The trade-off: you need to rebalance annually. Most plans offer auto-rebalance — turn it on and forget it.
3. The brokerage window — best for advanced users
Some plans (Schwab PCRA, Fidelity BrokerageLink) let you invest 401(k) money in nearly any ETF or fund. Useful if your plan's curated menu is bad. Risky if you use it to buy single stocks or sector bets.
The trade-off: more flexibility, more rope. Stick to broad-market ETFs (VTI, VXUS, BND) or you'll undo the simplicity gain.
Comparison: 401(k) fund types in April 2026
| Type |
Typical expense ratio |
Effort |
Best for |
| Index TDF (Vanguard/Fidelity Freedom Index) |
0.08–0.15% |
Zero |
Most people |
| Active TDF |
0.40–0.75% |
Zero |
No one, honestly |
| Index three-fund |
0.03–0.10% |
Annual rebalance |
DIY-inclined |
| Active equity fund |
0.50–1.20% |
Some |
Almost no one |
| Brokerage window ETFs |
0.03–0.20% |
Self-directed |
Advanced users |
| Stable value / money market |
0.30–0.50% |
Zero |
Within ~5 years of retirement |
Common mistakes to avoid
Holding too much company stock. Enron, Lehman, and a hundred quieter examples. Cap company stock at 5–10% of your 401(k), even if you love the company.
Stacking funds. Buying three TDFs and two index funds doesn't increase diversification — it just adds confusion. Pick one approach.
Picking by past performance. Last year's winner is rarely next year's. Pick by expense ratio and asset class, not the 1-year return chart.
FAQ
Roth or traditional 401(k)?
Traditional if you're in a high tax bracket today and expect lower in retirement. Roth if the reverse. Splitting 50/50 is fine if you don't know.
How often should I rebalance?
Once a year, or when an asset class drifts more than 5% from target. More frequent doesn't help.
Should I move 401(k) to IRA when I leave a job?
Often yes — IRAs have wider fund choices and lower fees than most 401(k)s. Rollovers are tax-free if done correctly.
Where to go next
For related guides see Target date funds explained for 2026, Best index funds in 2026, and What 1% fees cost you over 30 years (2026).