Inflation & Purchasing Power Calculator
See what money is worth over time: enter an amount, an annual inflation rate and years to get future cost, purchasing power and total erosion.
Enter an amount, an annual inflation rate and a number of years. You get what that same basket will cost later, and what today’s money will actually be worth once prices have climbed.填入一笔金额、年通胀率和年数，即可得到——同样一篮子商品未来的价格，以及在物价上涨之后，今天这笔钱实际还值多少。
Fill in all three fields to see how prices and purchasing power move.填入三个字段，即可看到价格与购买力的变化。
- Purchasing power购买力
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- Value lost损失价值
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- Erosion侵蚀比例
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- Total price rise价格总涨幅
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Money loses value when prices rise. Multiply an amount by (1 + inflation) for each year and you get the future cost — what the same basket of goods will run later. Divide instead and you get purchasing power — what today’s amount will actually buy after prices have climbed. Same rate, opposite directions.当物价上涨时，货币会贬值。把一笔金额按每年 (1 + 通胀率) 连乘，得到的是未来成本——同样一篮子商品日后要花的钱。反过来相除，得到的是购买力——在物价上涨之后，今天这笔钱实际能买到的东西。同一个利率，方向相反。
01The formula公式
Purchasing power = Amount ÷ (1 + i ÷ 100)n购买力 = 金额 ÷ (1 + i ÷ 100)n
Erosion = 100 × ( 1 − 1 ÷ (1 + i ÷ 100)n )侵蚀比例 = 100 × ( 1 − 1 ÷ (1 + i ÷ 100)n )
where i = annual inflation %, n = years其中 i = 年通胀率 %，n = 年数
Notice that erosion is never quite as large as the price rise. If prices climb 34%, purchasing power does not fall 34% — it falls to 1 ÷ 1.34, a loss closer to 25%. The two percentages describe the same gap seen from opposite ends, and the smaller one is always the drop in what your money buys.请注意，侵蚀比例永远不会和价格涨幅一样大。如果物价上涨 34%，购买力并不会下降 34%——而是降到 1 ÷ 1.34，损失更接近 25%。这两个百分比从相反的两端描述同一段差距，而其中较小的那个，始终是你的钱所能购买之物的下降幅度。
02A worked example一个算例
Suppose a basket costs $1,000 today, inflation runs 3% a year, and we look 10 years ahead.假设一篮子商品今天价值 $1,000，通胀率为每年 3%，我们展望 10 年之后。
- Growth factor = (1.03)10 = 1.3439增长系数 = (1.03)10 = 1.3439
- Future cost = 1,000 × 1.3439 = $1,343.92未来成本 = 1,000 × 1.3439 = $1,343.92
- Purchasing power = 1,000 ÷ 1.3439 = $744.09购买力 = 1,000 ÷ 1.3439 = $744.09
- Erosion = 100 × (1 − 744.09 ÷ 1,000) ≈ 25.6% — prices rose 34%, buying power fell 25.6%.侵蚀比例 = 100 × (1 − 744.09 ÷ 1,000) ≈ 25.6%——物价上涨 34%，购买力下降 25.6%。
So $1,000 stuffed in a drawer for a decade would still read “$1,000”, but it would stretch like $744 does now. The dollar figure never changed; what it commands did. That silent gap is what inflation actually costs.所以，把 $1,000 塞进抽屉存放十年，上面依然写着「$1,000」，但它的购买力只相当于今天的 $744。数字从未改变，改变的是它能买到什么。这段无声的差距，正是通胀真正的代价。
03The common trap常见陷阱
A frequent shortcut is to take “3% a year for 10 years” and subtract 30% of purchasing power. But inflation compounds — each year’s rise stacks on a base already lifted by the year before — so the price rise is 34%, not 30%. And because purchasing power is the reciprocal, the drop is 25.6%, not 30% either. Over long horizons or high rates the gap between the quick subtraction and the real math grows wide enough to change a plan.一个常见的捷径是把「每年 3%、共 10 年」直接减去 30% 的购买力。但通胀是连乘的——每一年的上涨都叠加在前一年已经抬高的基础之上——所以价格涨幅是 34%，而非 30%。又因为购买力是其倒数，下降幅度是 25.6%，同样不是 30%。在较长的时间跨度或较高的利率下，这种快速减法与真实计算之间的差距会大到足以改变一个计划。
04Where this breaks它的局限
This tool assumes one steady rate every year, which real inflation never obeys. A few honest limits:本工具假设每年都是一个稳定的利率，而真实的通胀从不遵守这一点。几点诚实的局限：
- A single average rate. Real inflation swings year to year. Use a long-run average as a rough guide, not a forecast of any single future year.单一平均利率。真实通胀逐年波动。请把长期平均值当作粗略参照，而非对某一具体未来年份的预测。
- Your basket isn’t the index. Headline inflation is an average across many goods. Rent, tuition and healthcare can run far hotter than the number, so your personal erosion may differ.你的篮子不是指数。公布的通胀是许多商品的平均值。房租、学费和医疗的涨幅可能远高于这个数字，因此你个人感受到的侵蚀可能不同。
- It ignores what the money earns. This is purchasing power on idle cash. Money invested at a return above inflation grows in real terms — the erosion here is the hurdle a return has to clear, not a verdict on saving.它忽略了资金的收益。这里算的是闲置现金的购买力。以高于通胀的回报进行投资的资金，其实际价值是增长的——此处的侵蚀是回报必须跨越的门槛，而非对储蓄的评判。
Inflation doesn’t shrink the number on the bill — it shrinks what the number can buy. Judge cash by its purchasing power, not its face value.通胀不会缩小账单上的数字——它缩小的是这个数字能买到什么。衡量现金要看它的购买力，而非它的面值。
See how a return can outrun inflation with the 用 compounding calculator复利计算器, or turn two values into a growth rate with the 看看回报如何跑赢通胀，或用 CAGR calculator年化增长率计算器.把两个数值换算成增长率。