We use cookies
MainRatios uses cookies for essential site functions. With your consent, we also use analytics cookies including session replay sampling (PostHog, Google Analytics) and advertising cookies (Google AdSense). You can reject non-essential cookies, including the "sale" or sharing of personal information under CCPA, and you may withdraw consent at any time (GDPR). See our Privacy Policy for details.
See how your investments grow over time with the power of compound interest. Adjust contributions, interest rates, and time horizon to project your wealth.
Amount of money you have available to invest initially.
Amount you plan to add each month.
Number of years you plan to invest.
Your estimated annual interest rate.
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which only earns returns on your original investment, compound interest allows your money to grow exponentially over time.
The math is powerful: even modest regular contributions can grow into substantial wealth given enough time and a reasonable rate of return.
The key insight is that time is your greatest asset. Starting early — even with small amounts — typically outperforms starting later with larger contributions. Explore our investment strategies to learn more about building long-term wealth.
A = P(1 + r/n)nt + PMT × [((1 + r/n)nt - 1) / (r/n)]
Example without contributions: $10,000 invested at 8% compounded monthly for 20 years grows to approximately $49,268 — nearly 5x your initial investment.
Example with contributions: Add $500/month to that same scenario, and the result jumps to approximately $344,000. Your total contributions would be $130,000, meaning compound interest generated over $214,000 in additional wealth.
Simple interest calculates returns only on the original principal. Compound interest calculates returns on the principal plus all previously accumulated interest. Over decades, the difference becomes enormous.
$10,000 at 8% for 20 years: