Retirement Calculator — Complete Guide
What this calculator does
The Retirement Calculator turns a handful of everyday numbers into a clear picture of your future: your current age, the age you want to stop working, the savings you already hold, the amount you add every month, an assumed annual return, and the income you hope to live on. It compounds all of that forward and shows the nest egg you are on track to build by the day you retire.
From that projection it derives three things people care about most. First, the target nest egg you would need to fund your desired lifestyle, with spending inflated to retirement and the widely used 25× rule applied. Second, the surplus or gap between what you are projected to save and that target. Third, the sustainable monthly income over your stated life expectancy using the real return after inflation.
The formula
years = retirement age − current age
r = annual return ÷ 12 ÷ 100
n = years × 12
future value = current savings × (1 + r)^n + monthly contribution × ((1 + r)^n − 1) ÷ r
target nest egg = expected annual spending × 25
gap = future value − target nest egg
sustainable monthly income = future value × 4% ÷ 12
The first term grows your existing savings with compound interest. The second term is an annuity: a steady stream of monthly contributions, each of which earns its own compounded return. Even modest monthly amounts become significant over decades, because the money you add in year one has thirty or more years to grow.
A worked example
Suppose you are 30, plan to retire at 65, already hold $50,000, add $500 a month, expect a 7% annual return, and want to spend $40,000 a year in retirement.
- Years to retirement: 65 − 30 = 35 years, so n = 420 months and r = 7% ÷ 12 ÷ 100 = 0.005833.
- Existing savings grow to: $50,000 × (1.005833)^420 ≈ $50,000 × 11.5 ≈ $575,000.
- Monthly contributions grow to: $500 × ((11.5 − 1) ÷ 0.005833) ≈ $500 × 1,800 = $900,000.
- Projected nest egg: $575,000 + $900,000 ≈ $1,475,000.
- Target nest egg: $40,000 × 25 = $1,000,000.
- Surplus: $1,475,000 − $1,000,000 = $475,000.
- Sustainable monthly income: $1,475,000 × 4% ÷ 12 ≈ $4,917.
In this case the plan is comfortably ahead of the target. Notice how much of the final balance comes from investment growth: the money you personally contributed is only $50,000 + $500 × 420 = $260,000, while growth supplies the other $1.2 million. Time, not the size of each deposit, does most of the heavy lifting.
Getting on track
- Start early. Every extra year of compounding changes the result more than a large one-off deposit later on.
- Raise contributions with your income. Saving a fixed percentage instead of a fixed amount keeps your pace as pay rises.
- Keep fees low. A 1% annual fee can quietly remove a large slice of your final balance over 35 years.
- Re-run the numbers whenever your spending target changes; the 4% rule is a planning guideline, not a guarantee.
- Treat this as one scenario, not a forecast — real returns vary year to year.
退休储蓄计算器完整使用指南
这个计算器能做什么
退休储蓄计算器把几个日常数字，变成一幅清晰的未来图景：你现在的年龄、计划停止工作的年龄、已经拥有的储蓄、每月追加的金额、假设的年化收益率，以及你希望在退休后过上的生活所需支出。工具会把这一切向前复利，给出你在退休当天预计能积累的资产规模。
基于这一个预测值，它接着推导出人们最关心的三件事。第一，为了支撑理想生活方式所需的目标资产，采用广为使用的 25 倍法则估算。第二，按当前计划预计能积累的资产与目标资产之间的盈余或缺口。第三，按 4% 提取率，你的资产预计能支撑的可支撑月收入。三者合起来，回答唯一真正重要的问题：我是否已经走在正轨上？
计算公式
年数 = 退休年龄 − 当前年龄
月收益率 r = 年化收益率 ÷ 12 ÷ 100
月数 n = 年数 × 12
未来资产 = 当前储蓄 × (1 + r)^n + 每月投入 × ((1 + r)^n − 1) ÷ r
目标资产 = 期望退休年支出 × 25
缺口 = 未来资产 − 目标资产
可支撑月收入 = 未来资产 × 4% ÷ 12
第一项让已有的储蓄随时间复利增长。第二项是一个年金：每月固定投入，每一笔都各自按复利累积收益。即使每月金额不大，经过几十年也会变得相当可观，因为第一年投入的钱有二三十年甚至更久的时间去滚雪球。
一个具体算例
假设你现在 30 岁，计划 65 岁退休，已有储蓄 50,000 元，每月追加 500 元，预期年化收益率 7%，希望退休后每年支出 40,000 元。
- 距离退休：65 − 30 = 35 年，因此 n = 420 个月，r = 7% ÷ 12 ÷ 100 = 0.005833。
- 现有储蓄增长为：50,000 × (1.005833)^420 ≈ 50,000 × 11.5 ≈ 575,000 元。
- 每月投入增长为：500 × ((11.5 − 1) ÷ 0.005833) ≈ 500 × 1,800 = 900,000 元。
- 预计退休资产：575,000 + 900,000 ≈ 1,475,000 元。
- 目标资产：40,000 × 25 = 1,000,000 元。
- 盈余：1,475,000 − 1,000,000 = 475,000 元。
- 可支撑月收入：1,475,000 × 4% ÷ 12 ≈ 4,917 元。
在这个例子里，计划明显领先于目标。请注意最终资产中有多大比例来自投资收益：你本人投入的资金只有 50,000 + 500 × 420 = 260,000 元，其余约 120 万元全部来自复利增长。真正出力的是时间，而不是每一次存款的多少。
如何走上正轨
- 尽早开始。多一年复利，比日后追加一大笔钱更能改变结果。
- 让投入随收入增长。按固定比例而非固定金额储蓄，收入上涨时节奏也能跟上。
- 控制费用。1% 的年费在 35 年里会悄悄吃掉最终资产中相当大的一部分。
- 当支出目标变化时重新测算；4% 法则只是规划参考，并非保证。
- 把这当成一个情景，而不是预测——真实收益每年都会波动。