You set the target mix — we do the maths to get there, contributions first.
Enter what you hold now and the allocation you are aiming for, and we show how far each part has drifted and exactly how to close the gap. New money is directed to your underweight targets first — the path that rebalances with no sales and no CGT event. Everything runs in your browser; nothing is uploaded, and there is no account.
Rebalancing is just bringing your portfolio back to the mix you decided on — but the how matters, because selling to rebalance can trigger capital gains tax. This free rebalancing calculator keeps you in control: you set the target weights (or start from a well-known third-party framework), you set the drift bands, and we simply do the arithmetic. It measures your total drift, flags which holdings are inside their band, approaching it, or out, and then builds the trade maths to get back on target — always directing any new contribution to your underweight targets first, since that rebalances with no sales and no CGT. It never tells you to buy, sell or hold; it shows the maths for the target you set, and you decide.
Based on the target you set, here's the maths to get there. You decide whether and what to trade.
These are well-known third-party allocation frameworks — a popular framework, not our advice. Pick one as a starting point, then adjust every number yourself.
Targets must total 100% (currently 0%).
Drift bands
We direct it to your underweight targets first — the zero-CGT path.
Add your current holding values and a target % for each (totalling 100%) — or pick a framework above — to see your drift and the maths to get there. Nothing is saved or sent anywhere.
Based on the target you set, here's the maths to get there. You decide whether and what to trade. This tool never tells you to buy, sell or hold — it shows the arithmetic for the target you set, and you decide.
Here is exactly how we turn your current holdings and your target mix into a drift reading and a trade plan — no recommendations, just the maths, with every step in plain English.
Measure how far each holding has drifted
We turn your current dollar values into percentages of your total, compare each against the target percentage you set, and report the gap in percentage points. The headline drift figure is the total-variation measure (the sum of the absolute gaps, halved) — the same single-number drift reading robo-advisers use.
Check each target against its drift band
A holding only needs tending once it drifts outside its band. Use a simple fixed band (±5 percentage points by default, editable per target) or switch on the 5/25 rule: targets of 20% or more use a ±5pp band, and smaller targets use ±25% of their own weight. In-band reads calm, approaching is a gentle nudge, out is flagged for action you choose.
Direct new money to the underweight targets first
If you are adding a contribution, we allocate it to your underweight targets before anything else — filling the biggest gaps first, then spreading the remainder by target weight, cents-exact and never selling. This is the zero-CGT path: buying with new money rebalances without crystallising a single capital gain.
Show the sell maths only where contributions cannot reach
If a holding is still over its band after contributions, we show how much you would need to trim to get back on target. It is the maths for the target you set — not advice to sell — and in the full portfolio tracker each suggested trim also carries its estimated capital gains tax, so the tax cost is visible before you act.
Rebalancing means bringing your holdings back to the target mix you chose after market moves have pushed them out of line. You compare each holding’s current weight to its target, decide how much drift you will tolerate (a “band”), and top up the underweight parts or trim the overweight ones once they fall outside the band. This calculator does the measuring and the arithmetic — you set the target and the bands, and you decide whether and what to trade. It is general information, not financial advice.
Often, yes — by directing new money instead of selling. If you have a contribution to invest, putting it into your underweight targets first nudges the mix back toward target without disposing of anything, so no capital gain is crystallised and no CGT event occurs. This calculator always allocates a contribution that way first, and only shows sell maths for holdings still over their band once the new money is spent. Selling always risks CGT, so the contributions-first path is the zero-tax one.
A drift band is how far a holding may stray from its target before you rebalance it — a tolerance that stops you trading on every small wobble. A common default is ±5 percentage points. The 5/25 rule, popularised by Larry Swedroe, sets the band for you: any target of 20% or more uses an absolute ±5pp band, while smaller targets use ±25% of their own weight (so a 4% target has a ±1pp band). You can use either here, and edit the fixed bands per holding.
That is your call — it depends on your goals, timeframe and risk tolerance, which is exactly why this tool never sets a house allocation. To help you start, we include several well-known third-party frameworks (shaped like popular diversified funds such as Vanguard’s Conservative-to-High-Growth range) with their growth/defensive split shown. They are popular frameworks, not our advice — pick one as a starting point and then adjust every number yourself. Consider a licensed financial adviser for a target tailored to you.
Completely. Every figure you enter is calculated in your own browser — nothing is uploaded, stored, or seen by us, and there is no login or email wall. It is free with no holding caps. For a version wired to your real holdings — with live prices, look-through ETF exposure and the estimated CGT on every suggested trim — our free portfolio tracker does the same maths on your actual book, still private to your browser.
Track your whole portfolio
See it on your real book: live prices, look-through ETF exposure, and the estimated CGT on every suggested trim — free, and private to your browser.
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