Portfolio rebalancing: bands vs calendar (a simple rule)
Rebalancing is just bringing your portfolio back toward your target weights. The question is when to do it. Two common methods are calendar rebalancing (e.g., every quarter) and band rebalancing (only when something drifts “enough”). For most beginners, you can combine both into one calm rule.
The two methods (in plain language)
1) Calendar rebalancing
You rebalance on a schedule: monthly, quarterly, or yearly. It’s simple and predictable.
- Pros: easy habit; prevents “never rebalancing”.
- Cons: can trigger unnecessary trades when nothing meaningful changed.
2) Band rebalancing
You rebalance only when an asset class moves far enough away from target. Example: target is 60/40 stocks/bonds, but stocks drift to 67% (or 53%).
- Pros: you trade only when there’s a reason.
- Cons: if you never check, you might also never rebalance.
A simple beginner rule that works well
Check on a calendar. Act only if bands are broken.
- Check frequency: quarterly is plenty for most long-term ETF investors.
- Band trigger: rebalance only if an allocation is off by ±5 percentage points (or more) from target.
Example: target 80/20 stocks/bonds. You check every quarter. If stocks are between 75% and 85%, do nothing. If stocks are 86% (or 74%), rebalance.
Why this combo is calm (and practical)
- You get a routine (so rebalancing isn’t forgotten).
- You avoid busywork trades when drift is tiny.
- You naturally tend to sell what went up and buy what fell — without trying to predict anything.
Three quick notes that prevent common mistakes
1) Use contributions first
If you add money regularly, the easiest “rebalance” is to direct new contributions toward the underweight asset. That often fixes drift with zero selling.
2) Don’t over-optimize bands
±5 percentage points is a good default. Tighter bands mean more trades; wider bands mean more drift. The exact number matters less than being consistent.
3) Write your rule down
A one-line rule beats motivation. Example: “Every quarter, if any asset is off target by ≥5 percentage points, rebalance back to target.”
Key takeaways
- Calendar tells you when to look.
- Bands tell you when to act.
- Quarterly checks + ±5pp bands is a calm default for long-term ETF portfolios.
Educational only, not investment advice.