About the Portfolio Rebalancing Calculator
This portfolio rebalancing calculator tells you exactly how much to buy or sell of each holding to get back to your target asset allocation. Enter up to five assets or funds with their current values and target percentages, plus any new cash you are adding. The calculator shows each asset’s current weight, how far it has drifted, the target value and the trade needed.
Choose a full rebalance, which buys and sells so every asset lands exactly on target, or a buy-only rebalance, which directs new money into the most underweight assets and avoids selling — useful in taxable accounts where selling would trigger capital gains. It works for any mix: stocks and bonds, individual funds, or a three-fund portfolio.
Targets should add up to 100%. If they do not, the calculator scales them proportionally and tells you. Trading costs, taxes and fractional-share limits are not included, so round trades to practical amounts.
With the default inputs, the total to buy is $10,000.00. Change any value above to recalculate instantly.
How to use the portfolio rebalancing calculator
- 1Name each holding or asset class and enter its current market value.
- 2Enter the target percentage for each; they should add up to 100%.
- 3Add any new cash you are investing now.
- 4Choose a full rebalance or buy-only with new cash.
- 5Place the buy and sell trades shown in the table.
Formula and method
For a full rebalance, each asset’s target value is its target weight times the portfolio total including any new cash. The difference from its current value is the trade: positive means buy, negative means sell. Buys and sells net out to exactly the new cash you add.
For a buy-only rebalance, the calculator first works out each asset’s shortfall below its target value. If the new cash covers every shortfall, it fills them and splits any remainder by target weight; otherwise it divides the cash in proportion to each shortfall, so the most underweight assets get the most money. Drift is measured in percentage points between current weight and target weight.
- Target %
- Desired share of the portfolio for an asset (scaled so all targets sum to 100%)
- Trade
- Amount to buy (+) or sell (−)
Worked examples
60/15/20/5 portfolio back to a 50/20/25/5 target
The $100,000 portfolio is 60% US stocks against a 50% target. Selling $10,000 of US stocks and buying $5,000 each of international stocks and bonds brings every asset to its target. Cash is already at 5%, so no trade is needed.
Buy-only rebalance with $8,000 of new cash
With $108,000 in total, international stocks need $6,600 more to reach 20%, bonds $7,000 more to reach 25% and cash $400 more to reach 5% — $14,000 of shortfall. The $8,000 is split in proportion: about $3,771 to international stocks, $4,000 to bonds and $229 to cash, with no sales.
Two-fund portfolio with targets that do not add to 100%
Targets of 60% and 30% add to 90%, so they are scaled to 66.7% and 33.3%. With $105,000 after new cash, the stock fund target is $70,000 (no trade) and the bond fund target is $35,000, so the $5,000 goes entirely to bonds.
Frequently asked questions
How often should I rebalance my portfolio?+
Common approaches are once a year on a set date, or whenever an asset drifts more than about 5 percentage points from its target. Rebalancing more often adds costs and taxes without much extra benefit for most investors.
Should I sell to rebalance or just add new money?+
In tax-advantaged accounts such as a 401(k) or IRA, selling has no tax cost, so a full rebalance is simple. In taxable accounts, directing new contributions and dividends to underweight assets avoids realising capital gains.
What is portfolio drift?+
Drift is how far an asset’s current weight has moved from its target because some investments grew faster than others. For example, a 60% stock target that has grown to 70% has drifted 10 percentage points.
Does rebalancing improve returns?+
Rebalancing is mainly a risk control: it stops your portfolio from becoming riskier than you intended as stocks outgrow bonds. It can help or hurt returns in a given period but keeps your risk level consistent.
Can I rebalance across multiple accounts?+
Yes. Treat all accounts as one portfolio, add up each asset class across them, and make the trades where they are cheapest — ideally selling inside tax-advantaged accounts.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.