# Rebalancing

> Rebalancing brings a portfolio back to its target weights after markets move. Learn calendar and threshold rebalancing, costs, taxes and the rebalancing premium.

Source: https://learn.tradelabsai.com/portfolio/rebalancing/  
Track: Portfolio and Performance · Level: Advanced · Updated: 2026-10-03  
Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice.  
Cite as: TradeLabs Learn, "Rebalancing", https://learn.tradelabsai.com/portfolio/rebalancing/

A portfolio set at 60% stocks and 40% bonds does not stay that way. When stocks rally, they grow to a larger share; when they fall, bonds take over. Over time, the portfolio's risk drifts away from what you chose. Rebalancing means trading back to the target weights, which usually involves selling what has risen and buying what has fallen. It keeps risk under control and enforces a disciplined, contrarian habit, but it costs trading fees and possibly taxes, so how and when to do it matters.

## How drift happens

**Example: A 60/40 portfolio after a stock rally**
A $100 portfolio holds $60 in stocks and $40 in bonds. Over a year, stocks rise 30% to $78 and bonds rise 2% to $40.80. The portfolio is now worth $118.80, with stocks at about 65.7%. To return to 60/40, the investor sells about $6.72 of stocks (from $78 to 60% of $118.80, which is $71.28) and buys the same amount of bonds, bringing bonds to $47.52. Without rebalancing, a few more strong years could push stocks above 75%, a much riskier portfolio than intended.

## Rebalancing methods

| Method | Rule | Pros | Cons |
|---|---|---|---|
| Calendar | Rebalance every quarter or year | Simple, predictable | Ignores how far weights have drifted |
| Threshold (bands) | Rebalance when a weight moves beyond a band, such as 5 points | Trades only when needed | Requires monitoring |
| Calendar plus threshold | Check on a schedule, trade only if outside bands | Balanced | Slightly more complex |
| Cash flow rebalancing | Direct new deposits or withdrawals to underweight assets | Low cost, tax efficient | Works only with regular cash flows |

Research by fund firms has generally found that rebalancing roughly annually, or when weights drift by around 5 percentage points, captures most of the risk control benefit without excessive trading.

## The rebalancing premium

When assets are volatile and not perfectly correlated, regularly rebalancing can add return compared with letting weights drift, because it systematically sells relatively high and buys relatively low. This effect, sometimes called a rebalancing bonus or diversification return, depends on assets mean reverting relative to each other. In strongly trending markets, rebalancing can reduce returns by trimming the winner too early. Its main, reliable benefit is risk control. See [Mean Reversion](https://learn.tradelabsai.com/strategies/mean-reversion/) and [Trend Following](https://learn.tradelabsai.com/strategies/trend-following/).

## Costs and taxes

| Cost | Ways to reduce it |
|---|---|
| Commissions and spreads | Use bands, rebalance less often, trade liquid funds. See [Transaction Costs](https://learn.tradelabsai.com/orders/transaction-costs/) |
| Capital gains taxes | Rebalance in tax advantaged accounts, use new contributions, harvest losses. See [Tax-Loss Harvesting](https://learn.tradelabsai.com/industry/tax-loss-harvesting/) |
| Market impact | Matters for large portfolios. See [Market Impact](https://learn.tradelabsai.com/orders/market-impact/) |

## Rebalancing for traders and strategies

The same logic applies to strategy allocations: a trading portfolio running several strategies drifts toward whichever performed best. Rebalancing risk allocations prevents one strategy from dominating. Volatility targeting is a related form: reducing exposure when volatility rises and increasing it when volatility falls. See [Risk Budgeting and Risk Parity](https://learn.tradelabsai.com/portfolio/risk-budgeting-and-risk-parity/) and [Volatility and ATR-Based Sizing](https://learn.tradelabsai.com/risk/volatility-and-atr-based-sizing/).

## Index rebalancing

Index funds rebalance when their index changes members or weights, which can create predictable trading flows around rebalancing dates. See [Index Rebalancing](https://learn.tradelabsai.com/fundamentals/index-rebalancing/).

## Common mistakes

1. **Never rebalancing,** letting risk drift for years.
2. **Rebalancing too often,** paying costs for little benefit.
3. **Ignoring taxes** in taxable accounts.
4. **Abandoning the plan** after a crash, when rebalancing means buying what has fallen. See [Loss Aversion](https://learn.tradelabsai.com/psychology/loss-aversion/).
5. **Forgetting all accounts:** rebalance the whole household portfolio, not each account separately.

## Frequently asked questions

### What is portfolio rebalancing?

Trading a portfolio back to its target weights after market movements cause it to drift, typically by selling assets that have risen and buying those that have fallen.

### How often should I rebalance?

Many investors rebalance once a year or when an asset class drifts about 5 percentage points from its target, which balances risk control and cost.

### Does rebalancing increase returns?

Sometimes, when assets move back and forth relative to each other, but its main benefit is keeping risk at the intended level.

Next, learn how optimisation chooses weights in [Portfolio Optimization](https://learn.tradelabsai.com/portfolio/portfolio-optimization/).

## Continue learning

- Next lesson: [Portfolio Optimization](https://learn.tradelabsai.com/portfolio/portfolio-optimization/)
- Previous lesson: [Factor Models](https://learn.tradelabsai.com/portfolio/factor-models/)
- Related: [Factor Models](https://learn.tradelabsai.com/portfolio/factor-models/): Factor models explain asset returns with common drivers such as the market, size, value and momentum. Learn CAPM, Fama French and how to run a factor regression.
- Related: [Asset Allocation](https://learn.tradelabsai.com/portfolio/asset-allocation/): Asset allocation decides how much to hold in stocks, bonds, cash, commodities and other assets. Learn the main approaches, a 60/40 example and how to choose a mix.
- Related: [Equal, Value and Volatility Weighting](https://learn.tradelabsai.com/portfolio/portfolio-weighting/): Compare equal weighting, market cap weighting and volatility weighting for portfolios. Learn how each works, worked examples and the strengths and drawbacks of each.
- Related: [Tax-Loss Harvesting](https://learn.tradelabsai.com/industry/tax-loss-harvesting/): Tax loss harvesting sells investments at a loss to offset gains while keeping similar exposure. Learn how it works, its real benefit and common mistakes.
- Related: [Transaction Costs](https://learn.tradelabsai.com/orders/transaction-costs/): Transaction costs include commissions, spreads, slippage, market impact and missed trades. Learn each part, how to estimate it and why it decides profits.
- Related: [Index Rebalancing](https://learn.tradelabsai.com/fundamentals/index-rebalancing/): Index rebalancing forces funds to buy additions and sell deletions. Learn how S&P 500 and Russell changes work, the index effect and closing auction flows.