Calculate exact buy/sell amounts needed to rebalance your portfolio to target allocation percentages across multiple holdings.
A portfolio drifts: when one asset outperforms, it silently grows past its target share. This calculator takes the current dollar value of each holding and a target percentage for each, then works out the precise trade list to get back on target. The arithmetic is a rebalancing within your existing total: underweight positions are funded by selling overweight ones, so the sell column and the buy column always balance. The thing most people miss is that with no new cash, rebalancing is a zero-sum shuffle - every dollar you add to an underweight holding must come out of an overweight one.
A concrete input and expected output from the current implementation.
Input
Current values: US stocks $60,000, International stocks $25,000, Bonds $10,000, Cash $5,000. Target percentages: US stocks 55%, International stocks 25%, Bonds 15%, Cash 5%.
Expected output
Total portfolio value: $100,000 US stocks: target $55,000 - sell $5,000 International stocks: target $25,000 - no change Bonds: target $15,000 - buy $5,000 Cash: target $5,000 - no change
Each holding's target value is the $100,000 total times its target percentage (55% of $100,000 is $55,000, and so on). The $5,000 US stock sale funds the $5,000 bond purchase, so no new money enters the portfolio.
For each holding the calculator computes target value = total portfolio value x target percentage, then subtracts the current value. A positive result is a buy order, a negative result a sell order, and a zero means the holding is already on target. Because the total is fixed, the sum of all buy amounts equals the sum of all sell amounts.
Target percentages must sum to 100 percent, because the calculator distributes one fixed total across the holdings. If they total more or less, the target values will not reconcile with the portfolio total, so check the sum before trusting the output. Enter values consistently - 55 for 55 percent, not 0.55 - and use one currency and one valuation date for all current values.
Only if you are adding new money. With no contribution, every buy must be funded by a sale because the total portfolio value is fixed. If you contribute regularly, buy only the underweight positions with the new cash and skip the sells; or add the contribution amount as a cash position and re-run to see how much selling it avoids.
The calculator only computes amounts; it does not decide timing. Common approaches are a fixed schedule, such as quarterly or annually, or a threshold rule, such as rebalancing when any position drifts more than 5 percentage points from target. Rebalancing too often in a taxable account adds trading costs and capital gains tax events.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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