Portfolio Rebalancing Calculator: When and How to Rebalance

Rebalancing brings your portfolio back to your target asset allocation after market movements push it off course.

If you target 60% stocks and 40% bonds, and stocks have a great year, your portfolio might drift to 70/30. You now carry more risk than intended. Rebalancing means selling some of the outperformer and buying the underperformer to return to 60/40.

Why Portfolios Drift

Markets do not move together. When US stocks return 25% and bonds return 3% in the same year, a $100,000 portfolio starting at 60/40 becomes:

| Asset | Starting | Return | Ending | |-------|----------|--------|--------| | Stocks ($60,000) | 60% | +25% | $75,000 | | Bonds ($40,000) | 40% | +3% | $41,200 | | Total | | | $116,200 |

New allocation: $75,000/$116,200 = 64.5% stocks. Drifted 4.5 percentage points toward equities.

After three good equity years, the drift can be 10+ percentage points, turning a moderate portfolio into an aggressive one.

Three Rebalancing Methods

Calendar rebalancing: Rebalance at set intervals (annually, quarterly). Simple and systematic. The downside: you might rebalance right after a major move that would have corrected itself, or wait too long after a large move.

Threshold rebalancing: Rebalance when any asset class drifts more than 5% from target. Triggers only when it matters. Requires monitoring but is more tax-efficient than calendar rebalancing.

Combination: Rebalance annually, but check thresholds quarterly. If thresholds are exceeded mid-year, rebalance then.

The Tax Cost of Rebalancing

In taxable accounts, rebalancing by selling winners triggers capital gains taxes. The rebalancing benefit needs to exceed the tax cost.

Example: $200,000 in stocks with $50,000 in long-term gains. Selling $15,000 to rebalance triggers $2,250 in tax at 15% capital gains rate.

Better alternatives in taxable accounts:

1. Redirect new contributions to the underweighted asset class instead of selling
2. Rebalance in tax-advantaged accounts (401k, IRA) where there are no capital gains taxes
3. Use dividends and distributions to buy underweighted assets
4. Tax-loss harvest in the same transaction to offset gains with losses elsewhere

In retirement accounts, rebalancing has no immediate tax consequences. Do it there first.

Does Rebalancing Improve Returns?

Rebalancing reduces risk by preventing drift toward excessive equity exposure. Whether it improves returns depends on which assets outperform over your specific period.

Research shows that rebalancing typically reduces portfolio volatility and max drawdown. It slightly reduces returns in prolonged bull markets (because you repeatedly trim the winner) but significantly reduces losses in crashes (because you held less of the overweighted asset at the peak).

For most investors, the volatility reduction is the primary benefit. Consistent with your target risk profile is the goal, not maximum returns.

Rebalancing Across Accounts

If you have multiple accounts (401k, Roth IRA, taxable brokerage), you can rebalance across the combined portfolio rather than within each account separately.

Strategy: Hold bonds in tax-deferred accounts (traditional 401k, IRA) and equities in taxable or Roth accounts. When rebalancing, sell bonds in 401k and buy more equity there, rather than selling equities in taxable accounts and triggering capital gains.

This asset location strategy lets you rebalance tax-efficiently by adjusting within the tax-advantaged accounts.

See Best Investing Platforms for platforms that offer automatic rebalancing.

Use the CalcMoney Investment Return Calculator to see how different allocation drift scenarios affect your long-term portfolio value.

Frequently Asked Questions

How often should I actually rebalance?

For most investors, once per year is sufficient. The difference between annual and quarterly rebalancing is small. Excessive rebalancing in taxable accounts costs more in transaction fees and taxes than the marginal benefit of staying more precisely on target.

Should I rebalance after a market crash?

Rebalancing after a crash means buying equities when they are depressed. This is the correct long-term move but psychologically hard. If your threshold triggers during a crash (your 60% equity target dropped to 50% equity), buying to get back to 60% requires deliberately increasing equity exposure when markets feel worst. This discipline is what produces the behavioral benefit of systematic rebalancing.

Does rebalancing work for international vs. US allocation?

Yes. If you target 70% US equity and 30% international, the same principles apply. International has underperformed US significantly over 2010-2024. Systematic rebalancing would have kept buying international during that period. Whether that patience pays off depends on future international performance, which remains uncertain.