Experience the magic of compound interest that grows exponentially over time. Enter your initial investment, monthly contributions, and expected rate of return to see your future asset value and compound interest effect at a glance.
The compound interest calculator is a tool that calculates the compound effect where interest earns interest over time. Called "humanity's greatest invention" by Einstein, compound interest brings tremendous wealth accumulation in long-term investments. Use this calculator to simulate your investment plan and set your wealth goals.
Enter the lump sum amount you can invest upfront. For example, if you have $10,000 saved, set it as your initial investment. The larger the initial investment, the greater the compound effect. However, even starting with a small amount, you can achieve substantial returns through consistent contributions and time.
Enter the amount you plan to invest additionally each month. Systematic investing helps smooth market volatility and lowers your average cost basis. Set a realistic amount based on what you can save from your monthly income. Even small amounts, when invested consistently, can build significant wealth through compound interest. If monthly contribution is 0, calculations will be based on initial investment only.
For annual return rate, enter the expected return of your investment product. Savings accounts offer 2-3%, bonds 3-5%, index funds 7-10%, and stocks are volatile but average 8-12% long-term. The longer the investment period, the more powerful the compound effect. We recommend minimum 5+ years for long-term investment. Simulate with 10, 20, or 30-year periods to truly appreciate the power of compound interest.
Compounding frequency is how often interest is added to principal. Monthly compounding applies the effect more frequently than annual compounding, resulting in slightly higher final amounts. Check the calculation results for final amount, total investment, and total earnings. The ratio of final amount to total investment is your return rate. Compare different scenarios (rates, periods) to develop an investment plan that suits you.
상황: A 28-year-old professional invests an initial $5,000 plus $500 monthly at 7% annual return for 32 years.
조건:
• Initial Investment: $5,000 • Monthly Contribution: $500 • Annual Return: 7% • Investment Period: 32 years (age 28 → 60)
결과:
• Total Investment: ~$197,000 • Final Amount: ~$740,000 • Total Earnings: ~$543,000 (275% return)
분석: Starting with a modest amount, after 32 years of compound growth, the investment becomes 3.7x the principal. Notice the "snowball effect" of compound interest where earnings accelerate dramatically in the final 10 years. The earlier you start, the better.
상황: When a child is born, invest $10,000 initially and add $300 monthly for 18 years.
조건:
• Initial Investment: $10,000 • Monthly Contribution: $300 • Annual Return: 6% • Investment Period: 18 years
결과:
• Total Investment: ~$74,800 • Final Amount: ~$129,000 • Total Earnings: ~$54,200 (72% return)
분석: By college enrollment, you'll have $129,000 for education expenses. Compared to simple savings, compound interest generates an additional $54,000. Compound interest is highly effective for goal-based long-term investing.
상황: Invest $50,000 retirement funds as a lump sum at 8% annual return for 20 years.
조건:
• Initial Investment: $50,000 • Monthly Contribution: $0 • Annual Return: 8% • Investment Period: 20 years
결과:
• Total Investment: $50,000 • Final Amount: ~$233,000 • Total Earnings: ~$183,000 (366% return)
분석: With long-term lump sum investment, compound interest alone multiplies assets 4.6x without monthly contributions. The larger the initial investment, the more powerful compound interest becomes. This is an ideal strategy for middle-aged investors with significant capital.
Simple interest is calculated only on principal, while compound interest is calculated on principal plus accumulated interest. For example, $10,000 at 10% simple interest for 10 years yields $20,000 (principal $10,000 + interest $10,000). But with compound interest, it becomes ~$25,940. The $5,940 difference is "interest on interest." This gap grows exponentially over time. At 20 years, simple interest yields $30,000, but compound yields $67,270—over 2x the difference. Compound interest is essential for long-term investing.
It depends on the investment product. Savings accounts offer 2-3%, safe but with low returns. Government or corporate bonds yield 3-5%. Index funds (S&P 500, broad market ETFs) average 7-10% long-term with balanced risk-reward. Individual stocks are volatile but can exceed 15% with good selection. Real estate varies by location and timing, ranging 5-15%. For beginners, targeting 7-8% annually with index funds is realistic. Higher returns come with higher risk, so choose based on your risk tolerance and goals. Past performance doesn't guarantee future results, so plan conservatively.
Monthly compounding is slightly more advantageous. Compound interest grows faster when interest is added to principal more frequently. For example, $10,000 at 10% for 10 years yields ~$25,940 with annual compounding but ~$27,070 with monthly compounding—a $1,130 difference. However, most financial products have fixed compounding frequencies, leaving little choice. Savings typically compound monthly, bonds annually, and funds depend on reinvestment timing. What matters more than compounding frequency is the "return rate" and "time horizon." Increasing annual return by 1% or extending investment period by 5 years has far greater impact than changing compounding frequency.
Yes, mid-term withdrawals significantly reduce compound effects. The core of compound interest is "reinvesting earnings," so withdrawing principal or gains eliminates opportunities for further compounding. For example, $10,000 at 10% for 20 years becomes ~$67,270, but withdrawing $5,000 at year 10 leaves only ~$43,640 at year 20—a $23,630 loss. Even accounting for the withdrawn $5,000, it's still a major loss. The best strategy for compound investing is to never touch it and maintain long-term. If you might need urgent funds, set aside an emergency fund (3-6 months living expenses) before investing.
You must subtract inflation to determine real returns. Long-term average inflation is 2-3% in many developed economies. If you invest at 7% return, real return is ~4-5%. For example, $20 million nominally in 20 years might have purchasing power of only $15 million due to inflation. Therefore, calculating with inflation-adjusted real returns is more realistic when planning investments. Low-return products like savings (2-3%) barely match inflation, meaning real wealth doesn't grow. To beat inflation, aim for minimum 5%+ annual returns, making stocks or real estate more favorable long-term.
Yes, compound interest calculators assume "constant return rates," but actual investments have fluctuating annual returns. Stock markets swing wildly—some years +30%, others -20%. Even with 7% long-term average, the actual path differs from calculations. Particularly, large early losses (-30%) significantly reduce compound effects, while large early gains (+30%) amplify them. This is called "sequence of returns risk." Also, taxes, fees, and inflation aren't reflected in calculators, so real returns may be lower. Compound calculators are "idealized simulations," so plan 10-20% conservatively for real investments. Still, the long-term compound effect itself doesn't disappear, so invest consistently.
The "Rule of 72" is a simple method to calculate how long it takes to double your investment. Divide 72 by annual return rate. For example, at 8% return, 72 ÷ 8 = 9 years to double. At 6%, it's 12 years; at 12%, it's 6 years. This rule helps easily understand compound effects. For instance, $10,000 at 10% becomes $20,000 in 7.2 years, $40,000 in 14.4 years, $80,000 in 21.6 years—growing exponentially. You can also reverse-calculate target timeframes with the Rule of 72. To grow $30,000 to $100,000 at 7% takes roughly 15 years (approximation based on doubling, not exact but close). It's a useful tool for investment planning.
This calculator is an idealized simulation assuming constant returns. Actual investments experience varying annual returns based on market volatility, economic conditions, and product characteristics, and may result in losses. Taxes (dividend tax, capital gains tax, etc.) and fees are not included, so actual returns may be lower. Past performance does not guarantee future results. Please invest prudently considering your risk tolerance and investment profile. All investments are made at your own risk, and these calculation results are for reference only.
복리(複利)는 원금에 발생한 이자가 다시 원금에 합산되어 그 합산된 금액에 또 이자가 붙는 방식입니다. 아인슈타인이 "세계 8번째 불가사의"라고 불렀다고 전해지는 복리는, 시간이 길수록 기하급수적으로 자산을 불려줍니다. 예를 들어 1,000만 원을 연 7%로 30년간 복리 투자하면 약 7,600만 원으로 7배 이상 불어납니다. 핵심은 '이자에 붙는 이자'의 눈덩이 효과입니다.
단리(單利)는 원금에만 이자가 발생하는 방식으로 계산이 단순하지만 장기 투자에서는 복리에 비해 수익이 크게 낮습니다. 1,000만 원을 연 10%로 20년간 투자했을 때, 단리는 3,000만 원이지만 복리는 약 6,727만 원으로 2배 이상 차이가 납니다. 투자 기간이 길수록 이 격차는 더욱 벌어지며, 10년보다 20년, 20년보다 30년에서 복리의 위력이 극대화됩니다. 장기 투자에서 복리 상품을 선택해야 하는 이유가 바로 여기에 있습니다.
복리 효과를 최대로 활용하려면 세 가지 원칙이 중요합니다. 첫째, 일찍 시작하세요. 20대에 월 30만 원씩 적립하면 30대에 시작하는 것보다 최종 자산이 2배 이상 차이 날 수 있습니다. 둘째, 꾸준히 유지하세요. 중간에 인출하면 복리의 눈덩이 효과가 크게 감소합니다. 셋째, 수수료가 낮은 상품을 선택하세요. 연 수익률 1%의 차이가 30년 후에는 수천만 원의 차이를 만들 수 있습니다. ISA, 연금저축, IRP 같은 세금 우대 계좌를 활용하면 세후 복리 수익을 극대화할 수 있습니다.