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Monthly Compound Interest · Annual Compound Interest · Rule of 72 · Annual ScheduleCompound Interest Calculator

If you enter the principal, annual interest rate, period, and compounding cycle, it immediately calculates the final amount, total profit, and the point at which the principal doubles (Rule of 72).

📈 Monthly/Yearly Compound Interest⚡ Rule of 72📋 Schedule by Year💰 Rate of Return Calculation
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📈 Enter compound interest information
principal10 million won
원
10,000250 million500 million750 million1 billion
Annual interest rate (yield)7.0%
%
0.1%7%15%22%30%
period20 years
년
1 year12 years25 years37 years50 years
Compound interest period
💡 The shorter the compounding period, the larger the final amount. Rule of 72 72 ÷ Annual Rate of Return = Time to double the principal
📊 Calculation result
📈

After entering the principal, interest rate, and period
Calculate Please press the button.

Final amount (compound interest)
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Total revenue—
Final amount of simple interest—
Difference between compound interest and simple interest—
Total return—
Annual average compound rate—
⚡ Rule of 72 — Double Your Principal
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What is a compound interest calculator?

Compound interest is a method where interest accrues on the principal, and then accrues again on that interest. It demonstrates such a powerful effect in long-term investing that Albert Einstein called it the “eighth wonder of the world.” Be sure to utilize this when reviewing long-term investment products such as stocks, ETFs, funds, pension savings, and IRPs.

Compound interest calculation formula

Final Amount = Principal × (1 + Annual Interest Rate ÷ n)^(n × Period)
n = Compound period(Monthly:12, Quarterly:4, Semi-annual:2, Annual:1)

What is the Rule of 72?

Double principal period (years) ≈ 72 ÷ Annual return (%)
Example: Annual return of 61 TP 3 T → 72 ÷ 6 = Principal doubles after approximately 12 years. If the annual return is 121 TP 3 T, it doubles in 6 years. Use this to set quick goals.

Differences by compounding cycle

Even with the same annual interest rate of 7%, the final amount varies depending on the compounding cycle. When investing 10 million won for 20 years: the annual compounding yields approximately 38.7 million won, while the monthly compounding yields approximately 40.06 million won, resulting in a difference of about 1.36 million won.

Why Compound Interest Is Important in Long-term Investment

  • The growth in assets in the latter 10 years is much greater than in the first 10 years.
  • The more you reinvest your profits (dividend reinvestment, interest reinvestment), the greater the compounding effect becomes.
  • A difference in annual return of 1 to 21 TP3T can create a difference of tens of millions to hundreds of millions of won after 30 years.

Frequently Asked Questions

What is the Rule of 72?
This is a quick way to calculate the time it takes for your principal to double. Dividing 72 by the annual rate of return (1 TP 3 T) gives you an approximate timeframe for doubling your principal. For example, with an annual rate of return of 81 TP 3 T, your principal will roughly double after 72 ÷ 8 = 9 years. Please use this calculator to verify the exact value.
How much is the difference between monthly and annual compounding?
Even with the same annual interest rate, the effective rate of return increases as the compounding period shortens. For example: If the annual rate of 121 TP3T is calculated using annual compounding, the return after one year is 121 TP3T; however, if calculated using monthly compounding, it is (1+0.01)^12 − 1 ≈ 12.681 TP3T, which is approximately 0.681 TP3Tp higher. As the period lengthens, this difference accumulates and becomes larger.
How does compound interest work in ETF or stock investments?
Reinvesting dividends or keeping earnings in the investment generates a compounding effect. For S&P 500 ETFs, the long-term average annual return when dividends are reinvested is known to be approximately 10–111 TP3T (in USD). Enter these return rates and timeframes into this calculator to simulate your target assets.
How is the real rate of return adjusted for inflation calculated?
Real rate of return ≈ Nominal rate of return minus inflation rate. If the annual compound interest is 71 TP3T and inflation is 31 TP3T, the real rate of return is approximately 41 TP3T. If you enter the real rate of return (41 TP3T) into the calculator, you can check the real increase in assets reflecting price increases.

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