CalcLibrary

Portfolio Rebalancing Calculator

Turn a portfolio snapshot into a practical rebalance plan. Enter each holding, set the target mix, add or remove cash if needed, and see what to buy, sell, or leave alone.

Examples

Winner needs trimming

Stocks ran ahead of plan, so the rebalance requires selling the oversized holding and topping up the laggards.

Portfolio State
{"holdings":[{"id":"us-stock","name":"US Stock ETF","currentValue":62000,"targetAllocation":50},{"id":"intl-stock","name":"International Stock ETF","currentValue":18000,"targetAllocation":20},{"id":"bonds","name":"Bond ETF","currentValue":14000,"targetAllocation":20},{"id":"cash","name":"Cash Reserve","currentValue":6000,"targetAllocation":10}],"netCashFlow":0,"toleranceBand":0}
Net Contribution / Withdrawal
$0
Tolerance Band
0 %
Adjusted Portfolio Total
$100,000.00
Current Portfolio Total
$100,000.00
Total Buys
$12,000.00
Total Sells
$12,000.00
Plan Status
Contribution helps, but sells are still required

Examples

Winner needs trimmingStocks ran ahead of plan, so the rebalance requires selling the oversized holding and topping up the laggards.$100,000.00
New cash does most of the workA fresh contribution goes into the underweight buckets first, reducing or eliminating the need to sell anything.$97,000.00
Edge: drift is visible, but still acceptableA small tolerance band lets tiny deviations stay untouched so you can avoid unnecessary trading.$100,000.00

How It Works

Formula

wi=ViPw_i = \dfrac{V_i}{P}

Ti=Padj⋅aiT_i = P_{adj} \cdot a_i

Δi=Ti−Vi\Delta_i = T_i - V_i

Padj=P+CP_{adj} = P + C

Variables

ViV_i

Current value of holding i

wiw_i

Current portfolio weight of holding i(%)

PP

Current total portfolio value

PadjP_{adj}

Adjusted total after contribution or withdrawal

aia_i

Target allocation for holding i(%)

TiT_i

Target value for holding i after cash flow

Δi\Delta_i

Trade delta; positive means buy, negative means sell

CC

Net cash flow; positive for contribution, negative for withdrawal

The calculator first totals your current holdings. It then adds any net contribution or subtracts any planned withdrawal to create an adjusted portfolio total. Each holding gets a target value from that adjusted total and its target allocation. The exact trade delta is the target value minus the current value. If you set a tolerance band, holdings already inside that band can be left alone and the remaining holdings absorb the rebalance work.

Tolerance is applied as a practical trading filter, not a forecast. Holdings already inside the tolerance band can be treated as “good enough” and left untouched. The remaining holdings are scaled to carry the rest of the rebalance so the plan still lines up with the adjusted portfolio total.

Frequently Asked Questions

01Why do portfolios drift away from the target mix?
Because holdings do not move in lockstep. A strong run in one asset, dividends landing in cash, or new money going into only one fund can all push weights away from the plan.
02When is contribution-only rebalancing enough?
When new cash can fill the underweight positions without leaving meaningful excess elsewhere. If the plan shows zero sells after your contribution, cash alone closed the gap for this rebalance.
03Why might tiny deviations not need action?
Small drifts often create friction without changing the portfolio much. A tolerance band helps you skip minor trades and focus on the positions that are meaningfully off target.
04Does this handle taxes, fees, or lot selection?
No. This calculator stays in planning mode only. It ignores taxes, trading fees, fractional-share limits, wash-sale issues, and account-specific rules.

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