Why this matters
Over time, portfolio drift is inevitable. One asset outperforms and grows beyond its target weight while another lags and shrinks below it. A portfolio that started as a balanced 60/40 stock-to-bond split can drift to 75/25 after a strong equity rally, exposing you to more risk than you originally intended. Rebalancing corrects this drift by selling the overweight positions and buying the underweight ones.
The mechanical act of calculating rebalance trades is tedious in a spreadsheet, especially with more than three or four assets. You need to compute each asset's current weight, compare it to the target, determine the dollar difference, and then figure out whether to scale buys and sells proportionally. A single arithmetic mistake throws off the entire rebalance and leaves your portfolio still misaligned.
This tool handles the entire computation instantly. You enter what you hold and what you want to hold, and it outputs the exact buy or sell amount for every asset. It also supports deploying new cash or withdrawing funds as part of the rebalance, which is how most people actually rebalance in practice — adding fresh capital to the laggards rather than selling winners.
Rebalance inputs and outputs
| Input | Description |
|---|---|
| Current holdings | Asset name and current dollar value for each position |
| Target allocation | Desired percentage for each asset (auto-normalized) |
| New investment | Positive = deposit, negative = withdrawal |
| Output per asset | Exact dollar amount to buy (positive) or sell (negative) |
How to use it
Add each asset you hold along with its current market value in dollars.
Set a target allocation percentage for each asset. The tool normalizes if the sum is not exactly 100.
Optionally enter a new investment amount to deploy alongside the rebalance, or a negative amount to model a withdrawal.
Review the output table showing exactly how much to buy or sell for each asset to reach your target weights.
Testing your result
Start with a simple two-asset portfolio. Enter BTC at $6,000 and ETH at $4,000 for a total of $10,000. Set targets to 50/50. The tool should tell you to sell $1,000 of BTC and buy $1,000 of ETH, bringing both to $5,000. Verify the sell and buy amounts sum to zero — you are not adding or removing capital.
Now add a $2,000 new investment. The new total becomes $12,000, so each asset should target $6,000. BTC needs no trade (already at $6,000 after receiving $0 from the new cash), and ETH needs a $2,000 buy. Test with targets that do not sum to 100 — enter 40/40 — and confirm the tool normalizes them to 50/50 with a warning.
Common mistakes
Forgetting that rebalance outputs are gross amounts that do not account for trading fees, which can be significant for small trades on low-liquidity pairs.
Entering current prices instead of current total values for each holding, which produces completely wrong weight calculations.
Setting target percentages that sum to something other than 100 and not noticing the normalization warning.
Rebalancing too frequently and paying excessive fees; most advisors recommend quarterly or when any asset drifts more than 5 percentage points from target.
Edge cases and options
When you enter a new investment, the tool distributes the cash proportionally to close the largest gaps first. A withdrawal is funded proportionally from each asset, so the post-withdrawal portfolio maintains the target allocation. This is cleaner than selling from a single asset to fund a withdrawal, which would re-introduce drift.
The tool does not account for slippage, trading fees, or tax implications of selling. Each sell trade in a taxable account may trigger a capital gains event. For crypto portfolios specifically, the tax treatment of each sell depends on your cost basis and holding period. Use the output as a plan, then subtract estimated fees before executing on your exchange.
Real-world use cases
A crypto investor with positions in BTC, ETH, and SOL that has drifted to 70/20/10 from a 50/30/20 target after a Bitcoin rally.
A monthly DCA investor who adds fresh capital each payday and wants to direct it toward underweight assets rather than buying proportionally.
A financial planner modeling a portfolio withdrawal for a client who needs to take $5,000 out while maintaining the target allocation across all positions.
Frequently asked questions
Q: Why should I rebalance my portfolio?
A: Over time, winners grow and your allocation drifts. Rebalancing sells overweight winners and buys underweight laggards, forcing you to buy low and sell high while keeping your risk profile consistent with your original plan.
Q: What if my target percentages do not sum to 100%?
A: The tool normalizes them automatically. If you enter 50/40/30, it treats them as roughly 41.7/33.3/25 and shows a warning that the raw sum was not 100.
Q: How do I model adding new cash during a rebalance?
A: Enter a positive value in the new investment field. That money gets allocated alongside the rebalance trades to reach the target. A negative value models a withdrawal, funded proportionally from each asset.
Q: Does this account for trading fees or taxes?
A: No. The output shows gross buy and sell amounts. Subtract estimated exchange fees from each trade and consider the tax implications of selling positions that have appreciated.
Q: How often should I rebalance?
A: Calendar rebalancing (monthly or quarterly) is simplest. Threshold rebalancing (when any asset drifts more than 5 percentage points from target) reduces unnecessary trades. Many investors combine both approaches.
Q: Can I use this for traditional stock and bond portfolios?
A: Yes — the math is identical regardless of asset class. Enter any holdings with their current values and target percentages. The tool works for stocks, bonds, ETFs, crypto, or any mix.
Start using it now
Try the Portfolio Rebalancer tool. See also DCA Calculator, Crypto Tax Calculator, and Investment Growth Calculator.
