← st-ox

Portfolio Rebalancing Calculator

Enter what you hold now and your target weights. The calculator shows exactly how much of each to buy or sell to get back on target — and you can add new cash to rebalance without selling.

AssetValue nowTarget %Action
Portfolio value: – To buy: – To sell: –

Amounts are in whatever currency you enter. Nothing you type leaves your browser. Add new cash to see a buy-only, tax-friendlier rebalance.

What is portfolio rebalancing?

You pick a target mix — say 60% stocks, 30% bonds, 10% gold. Then markets move. Stocks have a great year and suddenly they're 70% of your portfolio, carrying far more risk than you signed up for. Rebalancing brings each holding back to its target weight: trim what's grown too big, top up what's fallen behind. It's the single most reliable piece of portfolio maintenance there is.

Why bother?

The main reason is risk control, not extra return. Left alone, a portfolio quietly drifts toward whatever has run up most — usually the riskiest thing — right before it corrects. Rebalancing keeps your risk where you chose it. As a bonus, it forces a disciplined buy-low, sell-high habit: you're systematically selling what's expensive and buying what's cheap, without having to guess.

Two ways to do it

Many investors combine them: look once a year, but only trade the holdings that have drifted past the band.

Rebalance with new money to avoid tax

Selling in a taxable account can realise capital gains. A cleaner route is cash-flow rebalancing: point every new contribution and dividend at whatever is under target, so you buy your way back to balance instead of selling. Put a number in the “New cash to invest” box above and watch the sells shrink or disappear. When you must sell, doing it inside a tax-advantaged account avoids the tax hit entirely.

Frequently asked questions

What is portfolio rebalancing?
Buying and selling within your portfolio to bring each holding back to its target weight. Over time winners grow and losers shrink, so your allocation drifts; rebalancing trims what's grown too large and tops up what's fallen behind, restoring your intended balance of risk.
How often should I rebalance?
There's no single right answer. Common approaches are calendar rebalancing (once or twice a year) and threshold rebalancing (only when a holding drifts past, say, 5 percentage points from target). Rebalancing too often adds trading costs and, in taxable accounts, taxes.
How do I rebalance without selling anything?
Direct new money to your underweight holdings — "cash-flow rebalancing." Instead of selling winners, you use fresh contributions or dividends to buy whatever has fallen below target, restoring your allocation without triggering capital-gains tax. Use the "New cash to invest" field above to model it.
Does rebalancing improve returns?
It's mainly about controlling risk, not boosting returns. Its reliable job is keeping your portfolio's risk at the level you intended, and it enforces a buy-low, sell-high discipline. In some periods it helps returns slightly, in others it hurts slightly.
Is there tax on rebalancing?
In a taxable account, selling holdings that have gained can trigger capital-gains tax. To reduce it, rebalance inside tax-advantaged accounts where possible, or use new contributions to top up underweight holdings instead of selling. General information, not tax advice.

Rebalance your real portfolio in st-ox

st-ox pulls live prices for your actual holdings and tells you the exact whole-share trades to place to hit your targets — across US and European markets, in any currency. It can also load a ready-made model allocation for you. Free, no ads.

Open st-ox free →

For information and educational purposes only. Not investment or tax advice, and not a recommendation to buy or sell any security. The calculator runs entirely in your browser and stores nothing.