Compound Interest Calculator
Calculate compound interest growth over time with customizable principal, rate, compounding frequency, and monthly contributions. See detailed year-by-year projections.
Future Value
$37,405.09
| Year | Balance | Contributed | Interest |
|---|---|---|---|
| 1 | $11,962.16 | $11,200.00 | $762.16 |
| 2 | $14,066.16 | $12,400.00 | $1,666.16 |
| 3 | $16,322.27 | $13,600.00 | $2,722.27 |
| 4 | $18,741.46 | $14,800.00 | $3,941.46 |
| 5 | $21,335.54 | $16,000.00 | $5,335.54 |
| 6 | $24,117.15 | $17,200.00 | $6,917.15 |
| 7 | $27,099.84 | $18,400.00 | $8,699.84 |
| 8 | $30,298.15 | $19,600.00 | $10,698.15 |
| 9 | $33,727.66 | $20,800.00 | $12,927.66 |
| 10 | $37,405.09 | $22,000.00 | $15,405.09 |
All calculations run entirely in your browser.
Compound interest is often called the eighth wonder of the world — and for good reason. It is the mechanism that turns small, consistent investments into substantial wealth over time by earning returns not only on your initial principal but also on the accumulated interest from previous periods. Our free Compound Interest Calculator helps you visualize and plan for this growth with complete flexibility. Enter your starting investment amount, projected annual interest rate, investment timeframe in years, compounding frequency (daily, monthly, quarterly, semi-annually, or annually), and optional monthly contributions to model regular savings habits. The calculator instantly computes your future value alongside a detailed breakdown showing total amount invested versus total interest earned — revealing exactly how much of your final balance comes from compound growth. A year-by-year table tracks your balance progression, contributions over time, and accumulated interest at each milestone, making it an invaluable tool for retirement planning, education savings goals, investment portfolio projections, and any long-term financial planning scenario where understanding the power of compounding is essential to making informed decisions.
How Compound Interest Works
The power of compound interest comes from its self-reinforcing nature. Imagine you invest $10,000 at a 7% annual return. After year one, you earn $700 in interest, bringing your balance to $10,700. In year two, you earn 7% not just on your original $10,000 but on the full $10,700 — giving you $749 in interest instead of $700. This acceleration continues with each passing year, and the effect becomes dramatic over long time horizons. After 30 years at 7%, that same $10,000 grows to over $76,000 without adding another dollar. The compounding frequency matters significantly — more frequent compounding (daily or monthly versus annually) produces slightly higher returns because interest is calculated and added to the balance more often, giving new interest less time to wait before starting to earn its own interest. Adding regular monthly contributions supercharges this effect. Investing just $100 per month alongside the initial $10,000 at 7% for 30 years produces a final balance of approximately $197,000 — with over $83,000 coming purely from compound interest growth. This illustrates why starting early, even with modest amounts, and maintaining consistent contributions over decades, are the most reliable paths to building long-term wealth through the mathematical certainty of compound returns.
How to Use the Calculator
- Enter your initial investment — The starting principal — your lump sum deposit, current savings balance, or one-time investment amount.
- Set the annual interest rate — Use the expected annual return rate. For conservative estimates, 4–5% reflects bond or high-yield savings returns. For stock market projections, 7–10% represents historical average S&P 500 returns. For aggressive growth scenarios, you can model higher rates to understand best-case outcomes.
- Choose your time horizon — Enter the number of years you plan to let the investment grow. Longer time periods demonstrate the most dramatic compounding effects — the difference between 10, 20, and 30-year horizons is where the true power of compounding becomes visible.
- Select compounding frequency — Choose how often interest is calculated and added to your balance. Daily compounding produces the highest returns, followed by monthly, quarterly, semi-annually, and annually. Most savings accounts compound daily, while many investment accounts effectively compound continuously through market returns.
- Add monthly contributions — Model regular deposits to accelerate your growth. A small monthly contribution of even $50 or $100 can dramatically increase your final balance over long periods, demonstrating the strategy of dollar-cost averaging and consistent investing habits.
- Review your results — The Future Value shows your projected total balance. Total Invested reveals how much of that came from your own contributions, and Interest Earned shows the pure growth from compounding. The year-by-year table lets you track your progress at each annual milestone.