Portfolio Rebalancing Calculator
Portfolio drift is easy to miss because the account value can look fine while the risk mix quietly changes. This calculator starts with your current portfolio value, current stock or risk-asset weight, target weight, and any new cash. It then shows whether you need to buy or sell risk assets to return to target, plus the target dollar amounts after the new cash is included.
Trade needed
Sell risk assets
$9,000.00
Current drift from target
+12.0 pp
Target risk-asset value
$63,000.00
Target defensive-asset value
$42,000.00
Current risk-asset value
$72,000.00
Portfolio after new cash
$105,000.00
Uses simple allocation math before taxes, commissions, bid-ask spreads, fund minimums, and account restrictions. Treat it as a planning aid, not a recommendation to trade.
Why rebalancing is a risk-control tool
Rebalancing does not predict the market. It keeps the portfolio close to the risk level you chose before emotions took over. If a stock sleeve rises from 60% to 72%, the account may feel successful, but the next drawdown will hit a larger share of the portfolio. A target weight turns that decision into a rule instead of a reaction.
How to read the trade amount
The calculator treats the current risk-asset value as already invested. It adds any new cash to the total portfolio, applies the target weight to that new total, and compares the result with the current risk-asset value. A positive number means buying more risk assets. A negative number means selling or redirecting money toward defensive assets.
What it does not cover
This tool ignores taxes, commissions, spreads, account minimums, liquidity, and whether a trade belongs in a taxable account or a retirement account. It also does not say what your target allocation should be. Use it to make the arithmetic explicit, then apply your own investment policy and tax constraints separately.
FAQ
Should I rebalance with new cash first?
Often that is the cleaner first step because it can reduce the need to sell existing holdings. This calculator includes a new-cash field so you can see whether contributions alone bring the allocation closer to target.
What does percentage-point drift mean?
It is the current weight minus the target weight. A current weight of 72% against a 60% target is +12 percentage points, meaning the portfolio is 12 points overweight risk assets before rebalancing.
Does this choose the best stock or ETF to trade?
No. It works at the sleeve level, such as stocks versus defensive assets. Choosing which fund, stock, or lot to trade depends on taxes, liquidity, and your portfolio rules.
Evidence to read next
Use the calculator output with source-backed research, not as a standalone signal.
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