Calculate exact buy/sell amounts to rebalance portfolio to target allocation with tax-lot aware suggestions and drift alerts.
Enter your current holdings and the allocation you want, and this calculator returns the exact dollar amounts to buy and sell so each asset lands on its target percentage. Overweight positions are paired with underweight ones, so sells fund buys and the total stays put, and positions that drift past a tolerance you set are flagged for attention. What surprises most people: rebalancing usually means selling something that went up and paying tax on the gain, and the lot-level suggestions matter more than the headline numbers.
A concrete input and expected output from the current implementation.
Input
Portfolio total: $100,000 Target allocation: 50% stocks, 30% bonds, 20% cash Current holdings: stocks $62,000, bonds $25,000, cash $13,000
Expected output
Sell stocks: $12,000 Buy bonds: $5,000 Buy cash: $7,000 After the trades: stocks $50,000 (50%), bonds $30,000 (30%), cash $20,000 (20%). Sells total $12,000, buys total $12,000.
Stocks are $12,000 above their 50% target while bonds sit $5,000 below and cash $7,000 below. The single overweight funds both underweights, so the trades net to zero: 5,000 + 7,000 = 12,000, matching the sale exactly.
Each holding is measured against its target share of the total portfolio, and the difference becomes a dollar delta. Assets above target generate sell amounts; assets below generate buy amounts. The calculator pairs the two sides so total sells equal total buys, meaning the portfolio value stays unchanged and every dollar of a sale funds a purchase elsewhere.
When a sale is required, the tool works from the cost basis you provide for each lot, so you can order a sale to keep realized gains smaller or larger on purpose. Separate from that, it compares every position against its target and alerts on holdings that have moved beyond the tolerance you set, so you catch drift before it becomes a large, lumpy trade.
Only with new money. If you are adding cash, the calculator can direct the contribution to underweight assets until they reach target, no sales needed. With no new money, every purchase must be funded by a sale, and the overweight assets are the only source of funds, so selling is unavoidable.
Not always. Selling the highest-cost lots shrinks the realized gain today, but it leaves lower-basis shares that will realize larger gains later, and if you buy back a substantially identical security within 30 days, the wash-sale rule disallows the loss for now and defers it into the replacement shares' basis. Weigh the lot suggestion against your own tax situation before executing.
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