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Compound Interest Calculator
Simulate investment growth with compound interest.
Currency:
$
/mo
%
years
|
Final Amount
$15,095,030
Total Invested
$8,200,000
Initial $1,000,000 + Contrib. $7,200,000
Total Returns
+$6,895,030
Effective Return
84.1%
Profit Rate
84.1%
Principal
Returns
Principal: $8,200,000 (54.3%)Returns: $6,895,030 (45.7%)
Milestones Reached
$10,000,000... reached in year 15
Asset Growth Chart
Y1
Y20
Principal
Returns
Scenario Comparison
About Compound Interest
Compound interest means earning interest on both your principal and accumulated interest. Over long periods, this creates accelerating growth.
For example, investing 30,000 yen/month at 5% for 30 years yields ~24.97M yen from 10.8M yen in contributions -- about 14.17M yen in returns.
NISA: Tax-free investment account. Annual contribution limit of 1.2M yen for regular investment.
Taxable Account: Returns are taxed at 20.315% (15.315% income tax + 5% resident tax).
Rule of 72: Years to double your money = 72 / annual rate. At 5%, about 14.4 years.
* This simulation provides estimates only. Actual results vary with market conditions. Fees and expense ratios are not included.
📖How to Use
- 1Enter principal, annual rate, and investment period
- 2Optionally set monthly contributions for compound growth
- 3See final amount, total interest, and principal ratio in a chart
💡Tips & Knowledge
- •At 5% annual return over 20 years, your money grows to about 2.7x the principal
- •Rule of 72: years to double ≈ 72 ÷ annual rate. Compound interest grows exponentially over time
- •Even ¥10,000/month grows significantly over 30 years. Starting early is the biggest advantage
❓Frequently Asked Questions
Q.What is compound interest?
A. Compound interest means earning interest on both your principal and previously earned interest. This creates exponential growth over time — unlike simple interest, which only applies to the original principal.
Q.How does the investment period affect results?
A. The longer the period, the more dramatic the compounding effect. Starting 10 years earlier can more than double your final balance, which is why financial advisors say "time in the market" matters most.
Q.Should I account for inflation?
A. This calculator shows nominal (not inflation-adjusted) values. For real returns, subtract your estimated inflation rate (typically 2%) from the interest rate you input.
👉 Next Steps
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