Portfolio Rebalancing Bands Calculator

See how far your allocation has drifted, whether your rebalance trigger has been hit, and exactly how much to buy or sell to get back on target.

Inputs

Total portfolio value

The current total market value of your investment portfolio.

Target equity allocation

Your policy allocation to equities (stocks), expressed as a percentage.

Current equity allocation

The actual equity percentage in your portfolio right now after market movements.

Rebalance trigger band (±%)

Rebalancing is triggered when drift exceeds this threshold in either direction. A common rule of thumb is ±5%.

Expected equity annual return

Expected average annual return for the equity portion of your portfolio.

Expected bond/fixed annual return

Expected average annual return for the fixed income / bond portion of your portfolio.

Results update as you type, and the address bar keeps your numbers so the link you share reopens this exact calculation.

Equity to sell (negative = buy)

$50,000

Sell $50,000 of equity and move proceeds to bonds/cash to reach your 70% target.

Detailed results
Current drift from targetEquity allocation is 10.0% above target. Band is ±5%.	10%
Rebalance triggered? (1=yes)Drift of 10.0% exceeds the ±5% band — rebalance now.	1
Current blend expected returnWeighted blend: 80% × 9% + 20% × 4%.	8%
Target blend expected returnWeighted blend: 70% × 9% + 30% × 4%.	7.5%

What this result means

Your portfolio has drifted 10.0% from your 70% equity target — exceeding your ±5% band. To rebalance, sell $50,000 of equity and reinvest into bonds. Your current blended return expectation is 8.00% vs. 7.50% at target allocation.

5-Year Drift Projection (No Rebalancing)

Shows how your equity and bond allocations evolve year by year if you never rebalance, based on the expected returns for each asset class.

5-Year Drift Projection (No Rebalancing). 6 rows, first 6 shown.
Year	Equity %	Bond %	Equity Value	Bond Value
2,026	80%	20%	$400,000	$100,000
2,027	80.74%	19.26%	$436,000	$104,000
2,028	81.46%	18.54%	$475,240	$108,160
2,029	82.16%	17.84%	$518,012	$112,486
2,030	82.84%	17.16%	$564,633	$116,986
2,031	83.49%	16.51%	$615,450	$121,665

How this is calculated

equity_value = portfolio_value × current_equity_pct / 100
bond_value = portfolio_value × (1 − current_equity_pct / 100)
target_equity_value = portfolio_value × target_equity_pct / 100
drift_pct = current_equity_pct − target_equity_pct
needs_rebalance = |drift_pct| ≥ rebalance_band
equity_to_sell = equity_value − target_equity_value (negative = buy equity)
risk_adjusted_return = equity_pct × equity_return + (1 − equity_pct) × bond_return

Why rebalancing matters

Every portfolio has a target asset allocation — a planned mix of equities, bonds, and other assets that reflects your risk tolerance and investment horizon. Over time, because different asset classes grow at different rates, your actual allocation drifts away from that target. A portfolio set at 70% equity / 30% bonds might drift to 80/20 after a strong equity bull market. Without rebalancing, you end up taking on more risk than intended — or less, after a correction.

Rebalancing restores your portfolio to its policy allocation by selling what has grown disproportionately and buying what has lagged. Done consistently, it enforces buy-low, sell-high discipline at the asset-class level, which can improve risk-adjusted returns over long periods.

What is a rebalancing band?

There are two common rebalancing approaches: calendar rebalancing (rebalance every quarter or year regardless of drift) and threshold or band rebalancing (rebalance only when drift exceeds a set tolerance). Research generally favors threshold rebalancing because it acts when drift is actually material rather than on an arbitrary schedule.

The most widely cited rule of thumb is a ±5% absolute band. That means if your target equity allocation is 70%, you rebalance only when equity drifts below 65% or above 75%. This keeps you from over-trading in stable markets while still controlling risk during strong trends. Some investors use relative bands (e.g., ±20% of the target weight), which adapt proportionally to the target — useful for smaller asset-class slices.

The cost of not rebalancing

When equities outperform over multiple years, an unmanaged portfolio becomes progressively overweight in stocks. This feels good during bull markets but amplifies losses when the market corrects. A 70/30 portfolio that drifts to 85/15 behaves more like an aggressive growth portfolio: higher expected return, but significantly larger drawdowns. For investors near or in retirement, this is especially dangerous if they cannot afford to wait years for a recovery.

The drift cost in this calculator is expressed as the difference in blended expected returns between your current drifted allocation and your target allocation. A small return difference compounded over years can translate into meaningfully different risk profiles and sequence-of-returns outcomes.

Tax implications of rebalancing

Selling appreciated assets outside of tax-advantaged accounts (traditional or Roth IRAs, 401(k)s) triggers capital gains taxes. Long-term gains are taxed at preferential rates (0%, 15%, or 20% depending on income), but even those rates make unnecessary trading costly. Strategies to minimize the tax drag from rebalancing include: directing new contributions to underweight asset classes, rebalancing inside tax-advantaged accounts where gains are sheltered, harvesting tax losses to offset gains, and using dividends or interest received from overweight positions to fund purchases in underweight ones.

Rebalancing with new contributions first

The most tax-efficient rebalancing method is contribution-based rebalancing: whenever you add money to your portfolio, direct 100% of the new contribution to whichever asset class is currently underweight. This steers you back toward your target without creating any taxable event at all. For investors still in the accumulation phase with regular contributions (salary deferrals, monthly savings), this approach can often keep drift within the band without ever requiring a sell.

When contributions alone cannot close the gap — either because the drift is too large or you are in the distribution phase — a partial sale and repurchase is appropriate. Prioritize doing this inside tax-advantaged accounts first, then in taxable accounts with the least embedded gain.

Assumptions

The portfolio consists of two asset classes: equity and bonds/fixed income. Multi-asset portfolios with commodities, real estate, or international allocations require more complex rebalancing math.
Expected returns are constant and do not account for changing market conditions or valuation.
Transaction costs and bid-ask spreads from trading are not modeled.
Tax drag from selling in taxable accounts is not included in the return calculations.
The drift projection assumes no contributions or withdrawals during the projection period.
All calculations use annual compounding with end-of-year returns.

Frequently asked questions

›How often should I check if I need to rebalance?

For most long-term investors, checking quarterly is sufficient. With a band-based approach, you only act when drift exceeds your threshold — so frequent checking rarely leads to frequent trading. Checking too infrequently (annually or less) risks letting drift grow large before you catch it, especially in volatile markets.

›Is a 5% rebalancing band always the right choice?

Five percent is a widely used starting point, but the optimal band depends on your tax situation, transaction costs, and how much tracking error you can tolerate. Broader bands (7–10%) mean less frequent trading and lower costs but allow more drift. Narrower bands (2–3%) keep allocation tighter but may trigger excessive trading in volatile markets. For most taxable accounts, a 5% absolute band balances discipline and cost efficiency well.

›Should I rebalance in my taxable or tax-advantaged accounts?

Always rebalance inside tax-advantaged accounts first (IRA, 401k, HSA). Selling within these accounts does not create a taxable event, so you can freely adjust allocations without worrying about capital gains. Only move to taxable accounts if the required trade cannot be accomplished inside sheltered accounts, and then consider tax-loss harvesting to offset any gains realized.

›What happens to my risk if I never rebalance?

Over a long bull market for equities, a balanced portfolio will gradually become an equity-heavy portfolio. This increases expected return but also dramatically increases volatility and potential drawdown. An investor targeting 60/40 who never rebalanced during the 2010s equity run-up might have found themselves at 85/15 by 2020 — exposed to far more risk than their plan intended when the pandemic crash arrived.

›Can I use new contributions instead of selling to rebalance?

Yes, and this is the most tax-efficient approach. By directing all new contributions to the underweight asset class, you drift back toward target without triggering any taxable sales. This works best during the accumulation phase when contributions are large relative to the portfolio. As your portfolio grows, contributions become proportionally smaller and may not be enough to offset drift — at which point partial sales become necessary.