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Portfolio Rebalancing Calculator
See how far each holding has drifted from its target weight, and exactly what to buy or sell to get back on track.
How Rebalancing Works
The Calculation
Trade = Target Value − Current Value
Drift = Current Weight − Target Weight
A positive trade is a purchase, a negative one a sale. Drift is quoted in percentage points, so a holding targeted at 20% now sitting at 26% has drifted +6pp — not +30%.
Bands Beat Calendars
Rebalancing on a fixed date trades whether or not anything has moved. A tolerance band — say ±5pp — trades only when the portfolio has actually drifted, which usually means fewer transactions and lower costs for the same risk control. Set your band above and the calculator flags every holding outside it.
Rebalancing in a UK ISA or SIPP
No Tax on Disposals
Inside an ISA or SIPP, selling to rebalance triggers no capital gains tax, so the only cost is dealing charges and spreads. That makes a wrapper the natural place to do the selling half of a rebalance. In a General Investment Account a sale is a disposal, so contribution-only rebalancing is usually the cheaper route.
Set the Target First
This tool assumes you already know your target weights. If you do not, start with the portfolio allocation calculator to see where you stand today, or the mean-variance optimiser to derive a target from risk and return assumptions.
Want deeper insights?
This calculator rebalances a list of holdings you type in. ARIA imports your actual transactions from AJ Bell, Interactive Investor and Interactive Brokers, tracks drift across every account continuously, and tells you when a band is breached — instead of you checking by hand.
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