How does the rebalancer calculate buy and sell amounts?

It sums your current values plus any new cash to get the investable total, multiplies that total by each holding target weight to get a target value, then subtracts the current value. A positive result is a buy, a negative result is a sell. Adding new cash is handled automatically because it grows the investable total before the split.

What is a drift band and why use one?

A drift band (also called a tolerance band) is the percentage a holding can stray from its target before you bother trading. Set a 5% band and the tool only flags a buy or sell once a holding is more than 5 percentage points away from target. Bands cut trading costs and taxable events by ignoring tiny imbalances.

What does no-sell cash-flow mode do?

In no-sell mode the tool never tells you to sell. Instead it directs your new cash only to the holdings that sit below target, splitting it in proportion to how far each one is short. This is the tax-efficient way to rebalance a taxable account while you are still contributing.

How often should I rebalance my portfolio?

Common approaches are calendar-based (once or twice a year) or threshold-based (whenever a holding drifts past its band, often 5%). Research suggests rebalancing too often adds cost without improving returns, so an annual check combined with a drift band is a sensible default for most long-term investors.

Does it handle adding new money or withdrawing?

Yes. Enter a positive number in New cash to add to invest a fresh contribution, or a negative number to model a withdrawal. The investable total updates and every buy/sell amount is recalculated so the resulting weights still match your targets.

Is my portfolio data private and is this financial advice?

Everything runs in your browser and is stored only in your own local storage, so no values are ever uploaded. This is an arithmetic tool, not financial advice; it does not account for trading fees, spreads, taxes or minimum lot sizes, so treat its numbers as a starting point.

Portfolio Rebalancer

A portfolio rebalancer that converts your target asset allocation into the exact buy and sell amounts you need to place. List what you currently hold and what percentage you want each position to be, and the tool tells you, in money, how much to add to or trim from every holding to bring the portfolio back to plan. It is built for index-fund and ETF investors, anyone running a fixed stocks-and-bonds split, and DIY investors who add new money regularly and want to deploy it intelligently.

How it works

The calculator sums the market value of every holding to get your current total, then adds any new cash you intend to invest (or subtracts a withdrawal) to produce the investable total. It normalises your target percentages so they always represent a clean 100%, multiplies the investable total by each weight to get a target value, and subtracts the holding current value. A positive figure becomes a BUY, a negative figure becomes a SELL, and anything inside your drift band is left as a HOLD.

Two modes change the behaviour. A drift band suppresses trades smaller than the tolerance you set, so you are not churning the portfolio over a 1% wobble. No-sell cash-flow mode never recommends selling; it instead routes your new contribution to the most underweight holdings in proportion to how far each is below target, which is the standard tax-aware way to rebalance a taxable account while you keep contributing. A doughnut chart shows current weights against target weights side by side, and the summary reports total buys, total sells and your largest drift at a glance.

Example

Suppose you hold a 60/30/10 stocks, bonds and cash portfolio. Equities have run up, so your real split is 68/26/6 on a 21,000 balance. Enter those three values, set targets of 60, 30 and 10, and the plan tells you to sell roughly 1,680 of equities, buy about 840 of bonds and add about 840 to cash so each position lands back on its target weight.

Holding	Value	Now %	Target %	Action
Equities	14,280	68%	60%	Sell 1,680
Bonds	5,460	26%	30%	Buy 840
Cash	1,260	6%	10%	Buy 840

Switch on no-sell mode and add a 2,000 contribution instead, and the same tool splits that cash toward bonds and cash only, leaving equities untouched. Your inputs auto-save in this browser and never leave your device, and you can export the full plan as CSV or JSON for your records.