Percentage Gain/Loss Calculator
Percent gain or loss between two prices, the dollar profit or loss on your shares, and the gain needed to climb back to break-even.
Enter the price you bought at and the price you sold (or would sell) at. You get the percent change, the dollar profit or loss if you add a share count, and — on a loss — the gain you’d need to climb back to break-even.填入你的买入价与卖出价（或拟卖出价），即可得到涨跌幅；填入股数还能算出盈亏金额；若是亏损，还会显示要回到成本价所需的涨幅。
Fill in the buy and sell prices to see the percent change.填入买入价与卖出价即可查看涨跌幅。
- Dollar P/L盈亏金额
- —
- Gain to break even回本所需涨幅
- —
The percent change between two prices is the difference divided by the price you started at, times 100 — so a move from $50 to $60 is a $10 gain on a $50 base, or +20%. Multiply the raw dollar move by your share count for the profit or loss in cash. And when the result is a loss, the percentage that recovered it back to break-even is larger than the percentage you lost — a fact worth internalizing.两个价格之间的涨跌幅，就是差额除以起始价格再乘以 100——所以从 $50 涨到 $60，是在 $50 的基础上涨了 $10，即 +20%。把每股的价格变动乘以股数，就得到以现金计的盈亏。而当结果为亏损时，把它拉回成本价所需的涨幅，会大于你亏掉的跌幅——这一点值得牢记。
01The formula公式
Dollar P/L = ( Sell − Buy ) × Shares盈亏金额 = ( 卖出 − 买入 ) × 股数
Gain to break even = 100 × ( −change% ) ÷ ( 100 + change% )回本所需涨幅 = 100 × ( −涨跌幅% ) ÷ ( 100 + 涨跌幅% )
The break-even line only appears on a loss. It answers a different question than “how much did I lose”: it asks how far the lower price has to rise to reach your original cost again. Because the climb starts from a smaller base, the required gain always exceeds the loss — lose 20% and you need +25% back; lose 50% and you need +100%.回本涨幅一行只在亏损时出现。它回答的是与「我亏了多少」不同的另一个问题：更低的价格要涨多少，才能回到你最初的成本。由于起点更低，所需涨幅总是大于亏损幅度——亏 20% 需涨 +25%，亏 50% 则需涨 +100%。
02A worked example一个算例
Suppose a trader buys at $100.00 and later sells 200 shares at $50.00.假设一位交易者以 $100.00 买入，之后以 $50.00 卖出 200 股。
- Percent change = 100 × (50 − 100) ÷ 100 = −50.00%涨跌幅 = 100 × (50 − 100) ÷ 100 = −50.00%
- Dollar P/L = (50 − 100) × 200 = −$10,000盈亏金额 = (50 − 100) × 200 = −$10,000
- Gain to break even = 100 × 50 ÷ (100 − 50) = +100% — the $50 price must double to reach $100 again.回本所需涨幅 = 100 × 50 ÷ (100 − 50) = +100%——$50 的价格必须翻倍才能回到 $100。
The gain and the loss are not symmetric. Halving your money reads as a clean “−50%,” but undoing it takes a full double. This asymmetry is the quiet reason large drawdowns are so costly: the deeper the hole, the steeper the climb out.涨幅与跌幅并不对称。资金腰斩看上去只是干脆的「−50%」，但要弥补它却需要整整翻倍。这种不对称，正是大幅回撤代价高昂的隐秘原因：坑挖得越深，爬出来的坡就越陡。
03The common trap常见陷阱
A +50% gain followed by a −50% loss does not leave you flat. Start at $100, gain 50% to $150, then lose 50% of $150 — you land at $75, down 25%. Percentages compound off a moving base, so they can’t simply be added or subtracted across periods. To combine two moves, multiply the growth factors (1.5 × 0.5 = 0.75), not the percentages.先涨 50%、再跌 50%，并不会让你回到原点。从 $100 涨 50% 到 $150，再从 $150 跌 50%——你落在 $75，净跌 25%。百分比是在不断变动的基数上复利计算的，因此不能在不同时期间简单相加或相减。要合并两段变动，应把增长因子相乘（1.5 × 0.5 = 0.75），而非把百分比相加。
04Where this breaks它的局限
This is clean arithmetic on two prices. It stays honest only as long as those two prices are the whole story — and often they aren’t:这是对两个价格的干净算术。只有当这两个价格就是全部时它才诚实——而现实往往并非如此：
- Costs are ignored. Commissions, spread, slippage and taxes all sit between the quoted change and the money that actually reaches your account. A small percentage move can be entirely eaten by frictions.忽略了成本。佣金、买卖价差、滑点与税费，都夹在报出的涨跌幅和真正到账的钱之间。一次小幅变动，可能被这些摩擦成本完全吞掉。
- Dividends and splits. Raw price change misses cash paid out along the way, and a stock split changes the price without changing value — compare split-adjusted prices, not headline quotes.股息与拆股。单看价格变动，会漏掉期间派发的现金，而拆股会在不改变价值的情况下改变价格——应比较复权后的价格，而非表面报价。
- Percent ≠ dollars ≠ risk. A big percentage on a tiny position can matter less than a small percentage on a large one. Read the percent change alongside how much was at stake, not on its own.百分比 ≠ 金额 ≠ 风险。小仓位上的大百分比，重要性可能不及大仓位上的小百分比。要把涨跌幅与所投入的规模一并来看，而非孤立地读它。
A gain and the loss it reverses are never the same size — the smaller your base, the harder it works to climb back.一段涨幅与它所弥补的跌幅，从来不是同一个大小——基数越小，爬回原点就越吃力。
See how deep drawdowns compound in the 在 drawdown-recovery calculator回撤修复计算器, or study how gains and losses combine in the lesson on 中看看深度回撤如何累积，或在 risk, reward and expectancy风险、回报与期望值. 这节课中学习涨跌如何叠加。