Portfolio Rebalancing Calculator
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Enter each holding's current value and its target allocation to see how far your portfolio has drifted and the exact dollar amount to buy or sell in each position. Add new cash to invest and it is folded into the plan.
What portfolio rebalancing does
Over time the pieces of a portfolio grow at different rates. A strong run in stocks leaves you with more equity risk than you planned; a bond rally does the opposite. Rebalancing is the discipline of periodically trimming what has grown and topping up what has lagged so your allocation matches the risk level you originally chose.
This calculator turns that idea into concrete instructions. You tell it what you hold today and what mix you want, and it returns the precise dollar move for each holding — no spreadsheet formulas to wire up by hand.
The formula behind the numbers
The math is simple arithmetic applied consistently. First it sums every holding's current value to get your total, then adds any new cash you plan to invest to get the investable total.
For each holding the target dollar value is the target percentage multiplied by that investable total. The action is the target value minus the current value: a positive result means buy that amount, a negative result means sell it, and near-zero means hold.
- Total = sum of all current values
- Investable total = total + new cash
- Target value = (target % ÷ 100) × investable total
- Action = target value − current value (buy if positive, sell if negative)
When and how often to rebalance
There are two common triggers. Calendar rebalancing checks the portfolio on a fixed schedule — annually or quarterly is typical. Threshold rebalancing acts only when a holding drifts more than a set band, say five percentage points, from its target. Many long-term investors combine the two: check on a schedule, but only trade when drift is meaningful.
Rebalancing less often keeps costs and taxes down while still controlling risk. The 'Now %' column here shows your current drift so you can judge whether a trade is worth making at all.
Caveats worth remembering
Selling holdings in a taxable account can trigger capital gains tax, so where possible direct new contributions and dividends toward underweight assets instead of selling overweight ones — that is why the new-cash input exists. In tax-sheltered accounts like an IRA or 401(k) you can rebalance freely.
This tool ignores trading fees, bid-ask spreads, and taxes, and it assumes you can buy fractional amounts. Treat its output as a clear target to aim for, then round to whole shares and account for costs before placing orders.
Frequently asked questions
What is portfolio drift?
Drift is the gap between your current allocation and your target. If your plan is 60% stocks but a bull market pushes them to 68%, you have 8 points of drift and are carrying more risk than intended.
Can I add new money instead of selling?
Yes. Enter an amount in the new-cash field and it is added to your investable total. Underweight holdings then show larger buys, which lets you rebalance with fresh contributions and avoid selling.
How many holdings can I add?
As many as you like. Use the Add holding button to insert rows for every fund, stock, or asset class in your portfolio; the totals and targets update automatically.
Does it account for taxes or trading fees?
No. The amounts are pre-tax and pre-fee. In a taxable account, factor in capital gains before selling and prefer redirecting new cash to underweight positions.
Why does it warn that my targets don't total 100%?
An exact rebalance assumes your target percentages cover the entire portfolio. If they sum to more or less than 100%, the target values won't align with your total, so the tool flags it so you can correct the inputs.
What does 'Hold' mean in the action column?
It means that holding is already within a fraction of its target value, so no meaningful buy or sell is needed. You can leave it untouched.
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