The 5/25 Rebalancing Rule
Rebalance when: Any asset class drifts 5% from target, OR any position exceeds 25% of portfolio
This is the professional standard. It balances tax efficiency (you're not rebalancing constantly) with risk control (you catch drift before it compounds).
The Math: Too Often vs Too Rarely
Monthly rebalancing on a $1M portfolio costs roughly $500-1,000/year in trading fees plus capital gains taxes. But rebalancing never can cost you 10-15% in drift losses when a winning position runs away.
| Strategy | Frequency | Tax Cost | Drift Risk |
|---|---|---|---|
| Too Often (Monthly) | 12x/year | High | Low |
| Professional (5/25 Rule) | 3-5x/year | Moderate | Balanced |
| Too Rarely (Annual) | 1x/year | Low | High |
| Never | 0x/year | None | Very high |
How Drift Compounds
A 60/40 portfolio that drifts to 70/30 doesn't stop there. The next time equities rally, it could drift to 80/20. When you finally notice in your annual review, you're in a completely different portfolio than you intended.
The real cost isn't the rebalancing trade. It's the compounded risk of being off-target for months without knowing it. See how to monitor portfolio drift for the 3-step detection process.
Automated Monitoring Makes the 5/25 Rule Work
Manual rebalancing fails because you have to remember to check. Automated drift monitoring catches drift the moment it happens and alerts you. Then you decide:
- Rebalance now (if drift is above your 5/25 threshold)
- Wait and monitor (if drift is small and tax situation is unfavorable)
- Rebalance at year-end (batch rebalancing for tax efficiency)