What is compound interest?
Compound interest is interest calculated on the initial principal plus accumulated interest. This means you earn interest on your interest, creating exponential growth over time. It's the foundation of wealth building and long-term investment strategies.
How do I use this compound interest calculator?
Enter your initial investment (principal), annual interest rate, time period in years, and monthly contribution. Select your preferred compounding frequency (daily, monthly, quarterly, etc.) and click Calculate Growth to see your future balance with compound interest.
What is a good compound interest rate?
Historically, the S&P 500 has returned about 10% annually (before inflation). For conservative planning, 6-7% is realistic. High-yield savings accounts offer 4-5% as of 2025. Your expected rate depends on your risk tolerance and investment type.
How often should interest compound?
More frequent compounding yields slightly more growth. Daily compounding earns marginally more than monthly, which earns more than quarterly. However, the difference is small compared to the impact of your interest rate and time horizon.
What's the Rule of 72?
Divide 72 by your interest rate to estimate how long it takes money to double. At 7%, your money doubles in ~10.3 years (72÷7). At 10%, it doubles in 7.2 years. This rule provides a quick mental calculation for investment growth.
How do I maximize compound growth?
Start early to maximize time, invest consistently with monthly contributions, reinvest dividends, minimize fees, and avoid early withdrawals. Even small monthly additions make a massive difference over decades due to exponential growth.
What is the compound interest formula?
The formula is A = P(1 + r/n)^(nt) + PMT × [(1 + r/n)^(nt) - 1] / (r/n), where A is final balance, P is principal, r is annual rate, n is compounding frequency, t is years, and PMT is monthly contribution.
How much will my investment grow?
Use our compound interest calculator to see exactly how your investment will grow. Enter your initial deposit, regular contributions, interest rate, and time period to see the projected growth with a visual chart showing principal vs. interest.
How does monthly contribution affect compound interest?
Regular monthly contributions significantly boost your final balance through dollar-cost averaging. Consistent investing reduces timing risk and adds more principal that can compound, dramatically increasing your investment returns over time.
What's the difference between simple and compound interest?
Simple interest only earns on your initial principal. Compound interest earns on both your principal AND accumulated interest. Over long periods, compound interest produces exponentially higher returns, making it essential for wealth accumulation.
Can I use this for retirement planning?
Yes! This calculator is perfect for retirement planning. Enter your starting balance, expected monthly contributions, and anticipated return rate to project your retirement savings. Adjust the time horizon to see different retirement scenarios.
How does inflation affect compound interest returns?
Inflation reduces real returns. If your investment returns 7% but inflation is 3%, your real return is only 4%. For retirement planning, use conservative estimates (5-6% nominal returns) to account for inflation and ensure your purchasing power is maintained.