Portfolio Rebalancing Calculator
Work out the exact dollar buys and sells that pull your holdings back to their target weights, with optional new cash. Free, bilingual.
Enter what each holding is worth today and the weight you want it to carry. Add any new cash you’re putting in. You get the exact dollar buys and sells that pull the portfolio back to your targets.填入每个持仓当前的价值和你希望它占的比重，再加上你打算投入的新增现金，即可得到——把组合拉回目标权重所需的——每笔确切的买入与卖出金额。
Enter at least two holdings with a value and a target weight.至少填入两个持仓的价值和目标权重。
Rebalancing trades are the gap between what each holding is worth now and what it should be worth at your target weight. Add up every holding (plus any new cash), multiply that total by each target weight to get a dollar goal, and the difference from today’s value is your buy or sell. Positions that have run ahead get trimmed; positions that have lagged get topped up.再平衡交易，就是每个持仓现在的价值与它按目标权重应有价值之间的差额。把所有持仓（加上新增现金）相加得到总值，用总值乘以每个目标权重得到金额目标，与今天价值的差就是该买还是该卖。涨过头的持仓被减仓，落后的持仓被补仓。
01The formula公式
Target value = Total × Target% ÷ 100目标价值 = 总值 × 目标% ÷ 100
Action = Target value − Current value操作金额 = 目标价值 − 当前价值
Positive = buy · Negative = sell正值 = 买入 · 负值 = 卖出
Drift = Current% − Target%偏移 = 当前% − 目标%
Drift is how far a holding has wandered from its target weight — the number that tells you why a trade is needed. A holding at 60% of the book against a 50% target has drifted +10 points; the sell brings it home. Target weights should add up to 100%; if they don’t, the tool flags it rather than quietly assuming the rest is cash.偏移衡量一个持仓离目标权重漂移了多远——它告诉你为什么需要这笔交易。一个占组合 60%、目标为 50% 的持仓，偏移了 +10 个百分点；卖出把它拉回原位。目标权重应加总为 100%；若不满足，工具会提示，而不会默默假设其余是现金。
02A worked example一个算例
Suppose a trader holds $6,000 of A and $4,000 of B, and wants each at 50%. No new cash is added.假设一位交易者持有 $6,000 的 A 和 $4,000 的 B，希望两者各占 50%，且不投入新增现金。
- Total = 6,000 + 4,000 = $10,000总值 = 6,000 + 4,000 = $10,000
- A target value = 10,000 × 50 ÷ 100 = $5,000; action = 5,000 − 6,000 = −$1,000 → sell $1,000A 目标价值 = 10,000 × 50 ÷ 100 = $5,000；操作 = 5,000 − 6,000 = −$1,000 → 卖出 $1,000
- B target value = $5,000; action = 5,000 − 4,000 = +$1,000 → buy $1,000B 目标价值 = $5,000；操作 = 5,000 − 4,000 = +$1,000 → 买入 $1,000
- A had drifted to 60% (+10), B to 40% (−10). Selling $1,000 of A and buying $1,000 of B lands both at 50/50.A 已漂移至 60%（+10），B 至 40%（−10）。卖出 $1,000 的 A、买入 $1,000 的 B，两者回到 50/50。
Notice the trades net to zero here because no cash was added — every dollar sold funds a dollar bought. When you add new cash, the tool can often reach the targets by buying only, with no sells at all: fresh money flows first to the most underweight holdings.注意这里的买卖净额为零，因为没有投入现金——每卖出一元都用于买入一元。当你投入新增现金时，工具往往可以只靠买入达到目标、完全无需卖出：新钱会优先流向最被低配的持仓。
03The common trap常见陷阱
Every rebalance is a real transaction — it can trigger commissions, bid-ask spreads, and, in a taxable account, capital-gains tax on the winners you trim. Chasing an exact target after every small wiggle can quietly cost more than the drift it corrects. Many long-term portfolios rebalance on a schedule (say, once or twice a year) or only when a holding drifts past a set band (for example ±5 points), not on every fluctuation. This tool shows the trades; whether the drift is worth acting on is a separate judgment about cost and taxes.每一次再平衡都是一笔真实交易——可能产生佣金、买卖价差，在应税账户中还会对减仓的盈利部分征收资本利得税。每有小幅波动就去追求精确目标，其代价可能悄然超过它所纠正的偏移。许多长期组合按固定周期再平衡（比如每年一到两次），或只在持仓偏移超出设定区间（例如 ±5 个百分点）时才动手，而非每次波动都调整。本工具展示交易金额；这点偏移是否值得动手，是关于成本与税务的另一重判断。
04Where this breaks它的局限
The math splits a total cleanly into target slices. It does not know the frictions of moving real money. A few honest limits:这套算法能把一个总值干净地切成目标份额，但它并不了解真实资金流动中的摩擦。几点诚实的局限：
- Whole shares and lot sizes. A $1,000 buy of a $340 stock isn’t exactly three shares. Real orders round to whole shares (or fixed lots), so you’ll land near the target dollar amount, not precisely on it.整股与最小交易单位。用 $1,000 买一只 $340 的股票并不正好是三股。真实下单要取整到整股（或固定手数），因此你只能落在接近目标的金额附近，而非精确命中。
- Taxes and costs aren’t modeled. The action amounts are pre-tax and pre-fee. In a taxable account, selling a winner to rebalance can realize a gain; weigh that before trimming.未计入税费。操作金额是税前、费前的。在应税账户中，为再平衡而卖出盈利持仓可能实现应税收益；减仓前请权衡这一点。
- Target weights, not a view. This tool executes the weights you type — it takes no position on whether those weights are wise. Deciding the target allocation is the harder, prior question.只是目标权重，而非观点。本工具执行你填入的权重——它不评判这些权重是否明智。决定目标配置本身，是更难、更靠前的一步。
Rebalancing sells what has grown and buys what has lagged — a discipline, not a forecast. The trades are simple; the judgment is when they’re worth the cost.再平衡卖出涨多的、买入落后的——这是一种纪律，而非预测。交易本身很简单；难的是判断何时值得为之付出成本。
Size each new buy with the 用 position size calculator仓位计算器, or read the lesson on 为每笔新买入定仓，或阅读关于 position sizing仓位管理. 的课程。