Compound Interest Calculator - Investment Growth & Rule of 72

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计算器
Compound Interest Calculator

What is "Compound Interest"?

Compound interest means returns are added back into your balance so future returns grow on both principal and past gains.

Example: $10,000 at 7% for 20 years grows to about $38,700 before fees and taxes.

复利计算器

初始投资¥60,000.00

月度存款¥3,000.00

年利率（%）

0%10%20%

投资期限（年）

1y25y50y

Last Year Rate Assumption (%)

Used for the "this year vs last year" simulation.

复利频率Results update in real time when you move the rate/term sliders.

总投资额

¥780,000.00

78万元

总利息收入

+102万元

最终金额 🚀

(180万元)

Investment Return Grade

🌟 A

优秀

综合得分58/100

预计前前 20%

* 与普通平均值比较的估算值

增长图表

You vs Average

Benchmark: U.S. long-term average return assumed at 7%

Final gap: +¥0.00

This Year vs Last Year

Compares one-year outcomes using current and last-year return assumptions.

End-of-year difference: +¥808.00

💰

Compound Interest Result

¥1,805,104.00

✨ Estimated interest: ¥1,025,104.00

Expected value after 20 years (7% annual return)

🎉 与朋友分享！

分享您的结果并与朋友比较

#CompoundInterest #Investment #Finance #WealthBuilding

💸What if I keep this for retirement?

👉 Calculate my retirement asset and monthly pension

什么是复利？

复利是对本金和以前期间积累的利息一起计算的利息。与仅对本金计算的单利不同，复利使您的资金随时间增长更快。

复利计算公式

A = P(1 + r/n)^nt

A = P(1 + r/n)^(nt)，其中A是最终金额，P是本金，r是年利率，n是每年复利次数，t是年数。

72法则

72法则是估算投资翻倍时间的简单方法。用72除以年回报率即可得到大约的年数。例如，在6%的年回报率下，您的投资将在约72÷6=12年内翻倍。

At 7% return, your investment doubles in about 10.3 years.

How to Read the Comparison Features

"You vs Average": See whether your assumptions outperform or underperform a U.S. long-term baseline.
"This Year vs Last Year": Quantify how a rate change shifts your one-year ending value under the same contribution plan.
Rate and term sliders update charts in real time so you can test scenarios quickly.

复利投资建议

✓尽早开始投资以最大化复利增长
✓定期投入，即使是小额也会积少成多
✓将收益再投资以加速增长
✓长期投资获得最佳结果

Last updated: 2025-01

📝 How to Use

Enter Initial Investment

Input your starting principal amount.

💡 Starting small is okay - consistency matters!

Set Annual Return Rate

Enter expected annual return rate (%).

💡 Stock funds average 7-10%, savings 2-4%.

Choose Investment Period

Enter how many years you plan to invest.

💡 Compound effect accelerates after 10 years!

Add Monthly Deposits (Optional)

If you plan to add money monthly, enter the amount.

💡 Regular contributions maximize compound growth.

谁适合使用这个工具？

先看适合的人群和典型使用场景。

🎯

Best-fit users

Useful when you want numbers around 401(k), ETF, and savings goals.

DecisionFit

📊

Comparison-first users

Helpful when you need to compare your current setup against a realistic alternative.

CompareChoice

💸

Cash-flow aware users

Good when sustainability matters more than the headline number.

Cash FlowReality

🧭

People who need a baseline

Start here when you want a numeric baseline before taking action.

BaselinePlanning

示例计算

用具体数字判断什么时候最值得使用。

Scenario 1

Run a realistic baseline first

Result

See the first decision threshold quickly

A rough baseline is better than guessing.

Scenario 2

Change one major variable

Result

Watch how decision quality changes

Structure often matters more than the headline number.

Scenario 3

Use a more conservative assumption

Result

Stress-test the plan before committing

Conservative assumptions usually create better real-world plans.

相似情况对比

把 X vs Y、能负担多少、什么时候更划算放在一起看。

打开对比工具

X vs Y

Best for

When two choices look similar on the surface

Watch for

The hidden structure often matters more than the headline number.

Decision rule

Cash flow and sustainability usually matter more than optics.

How much is really affordable?

Best for

When approved amount and healthy amount are not the same

Watch for

Maximum eligibility is rarely the same as safe capacity.

Decision rule

Set the monthly burden you can carry first, then build around it.

When is this favorable?

Best for

When timing or conditions change the answer

Watch for

Delay can become more expensive than expected.

Decision rule

Prepared structure and consistency usually beat perfect timing.

💡

Expert Tip

The key to compound interest is 'time'. If you start investing $300/month at 30, someone starting at 40 can't catch up even with $1,000/month. The best time to invest was 10 years ago. The second best time is now.

— Warren Buffett's Investment Philosophy

常见问题

What should I look at first in this calculator?

Start with the assumption that changes the result most. This tool is most useful for setting a decision baseline, not pretending the first number is perfect.

How do I use the compound interest calculator?

Just enter your initial investment, annual return rate, and investment period. Optionally, you can add monthly contributions. The calculator shows your final amount, total interest, and yearly growth chart.

💡 Adding monthly deposits supercharges your compound growth!

What is the Rule of 72?

Divide 72 by your annual return rate to estimate how long it takes to double your money. For example, at 8% return: 72÷8=9 years to double your investment.

💡 Our calculator automatically shows you the Rule of 72 result!

What is the difference between simple and compound interest?

Simple interest applies only to principal, while compound interest applies to principal + accumulated interest. $10,000 at 5% for 20 years: simple interest = $20,000, compound = $26,500. The longer you invest, the bigger the difference.

💡 This is why compound interest is called "interest on interest"!

What is a realistic annual return rate?

It varies by investment: Savings 2-4%, Bonds 3-5%, Stock ETFs 7-10%, Individual stocks vary widely. For long-term planning, 7% is a conservative and realistic estimate.

💡 Remember: higher returns usually mean higher risk!

How early should I start investing?

The earlier, the better! Starting at 25 with $200/month at 7% gives you ~$550,000 by 65. Starting at 35 with the same amount yields only ~$250,000. A 10-year difference makes more than 2x difference!