The full guide
Portfolio rebalancing: turn target weights into a disciplined trade plan
By TaprobaneFi Research Desk · Reviewed and updated July 20, 2026 · Global educational edition
Market movements cause a portfolio's asset weights to drift away from its chosen allocation. Rebalancing calculates the purchases and sales that would restore target weights at current values. It is a risk-control process, not a prediction about which asset will perform best next.
The current tool accepts three asset sleeves, their current values, and target percentages. It can also apply an absolute percentage-point drift band. It ignores taxes, transaction costs, security lots, and account restrictions, so its trade amounts are planning estimates rather than executable instructions.
From current values to trade deltas
Current weight equals a sleeve's value divided by total portfolio value. Target value equals total portfolio value multiplied by the sleeve's target percentage. The suggested trade is target value minus current value: a positive number indicates a purchase and a negative number indicates a sale.
Target percentages must sum to 100% for the trades to represent a fully allocated, zero-net rebalance. The interface withholds trade deltas when the total differs, so correct the targets to 100% before interpreting a trade list.
Worked three-sleeve example
Suppose equities are worth 42,000, bonds 22,000, and cash 6,000, for a 70,000 total. The current weights are 60.0%, about 31.4%, and about 8.6%. Against targets of 60%, 35%, and 5%, equities need no trade, bonds are below target, and cash is above target.
The mathematical rebalance moves 2,500 from cash to bonds. Purchases and sales net to zero because the target weights total 100%. Real accounts may require rounded units or retain a minimum cash balance, which changes the executable amounts.
| Sleeve | Current value | Target value | Suggested direction |
|---|---|---|---|
| Equities | 42,000 | 42,000 | No trade |
| Bonds | 22,000 | 24,500 | Buy 2,500 |
| Cash | 6,000 | 3,500 | Reduce 2,500 |
How the drift band works
Advanced mode compares the absolute difference between current weight and target weight with the selected band. A 5% band means five percentage points, not 5% of the target. A sleeve targeted at 40% is flagged at 45% or 35% under that rule.
A band avoids trading for small movements. The calculator still shows the full amount needed to return to target once a sleeve is flagged; it does not calculate the smaller trade needed merely to reach the edge of the band.
Calendar, threshold, and cash-flow rebalancing
Calendar rebalancing reviews the allocation at a fixed interval. Threshold rebalancing acts when drift crosses a defined band. A hybrid can review periodically while trading only after a threshold is breached. The rule should be selected before market stress, then applied consistently.
New contributions, distributions, and withdrawals can often reduce drift without selling. Directing new money to underweight sleeves may lower tax and transaction friction. This client does not include new cash as a separate input, so calculate the post-contribution values before entering them.
Translate the mathematical plan into an executable one
Holdings across several accounts may belong to one allocation even when they cannot all be traded in the same place. Define the portfolio boundary, valuation time, and asset classification before calculating.
Pre-trade checks
- Confirm target weights total exactly 100%.
- Use current values captured at a consistent valuation time.
- Check taxes, spreads, commissions, minimum trade sizes, and available lots.
- Use contributions and withdrawals to offset drift where practical.
- Record the reason for any deliberate deviation from policy.
Limitations and responsible use
The tool supports exactly three rows and does not add or remove holdings. It does not optimize taxes, select lots, estimate transaction costs, enforce a cash floor, or coordinate account restrictions. It also does not determine suitable target weights.
Use it after an allocation policy has been chosen, not to create that policy. Verify all target totals and practical constraints before trading. The output is educational portfolio arithmetic, not personalized investment advice.
Sources & further reading
This guide is educational. Calculator outputs depend entirely on the assumptions entered and do not predict investment returns, inflation, fees, taxes, or market conditions. Rules and product terms differ by country; verify any decision with current primary sources and an appropriately qualified professional. Nothing here is financial, tax, legal, or investment advice.