Compound Interest Calculator
See your money grow over time · Updated 2026
The Power of Compound Interest
Compound interest is the process where your investment earnings generate their own earnings — creating exponential growth over time. Einstein reportedly called it the “eighth wonder of the world.”
The key variables: principal (how much you start with), contribution (how much you add regularly), return rate (how fast it grows), and time (how long you let it compound). Time is the most powerful variable — starting 10 years earlier can double your final balance.
How Compounding Works
The formula is: FV = P(1+r)^t + C×((1+r)^t-1)/r where P is principal, C is annual contribution, r is return rate, and t is years.
At 7% returns, your money doubles roughly every 10 years (the Rule of 72: 72/7 ≈ 10.3). This means a $10,000 investment becomes $20,000 in 10 years, $40,000 in 20 years, and $80,000 in 30 years — without adding a single dollar.
| Years | Value |
|---|---|
| 10 years | $19,672 |
| 20 years | $38,697 |
| 30 years | $76,123 |
| 40 years | $149,745 |
| 50 years | $294,570 |
How to Maximize Compounding
1. Start early — a 25-year-old investing $5,000/year at 7% will have ~$1M by 65. A 35-year-old starting the same plan will have ~$472K.
2. Invest consistently — automate contributions. Dollar-cost averaging smooths out market volatility.
3. Minimize fees — a 1% fee can consume 28% of your returns over 30 years. Use low-cost index funds (0.03-0.15% expense ratios).
4. Reinvest dividends — dividend reinvestment adds roughly 1.5-2% to your annual compounding.
References
Frequently Asked Questions
How is compound interest calculator calculated?
The formula is: P(1+r)^t + C×((1+r)^t-1)/r. Enter your values above and click Calculate to see your personalized result instantly. Compound interest is the eighth wonder of the world. Starting with $10,000 and adding $5,000 annually at 7% return, after 20 years you'll have over $240,000 — and nearly half of that growth comes…
What inputs do I need for the compound interest calculator?
You need: Principal, Contribution, Rate, Years. Default values are pre-filled — adjust them to match your personal finances for a customized result.
Is the compound interest calculator free to use?
Yes — all TorchFI calculators are completely free. No registration, no email required. Calculations run entirely in your browser for maximum privacy. We never see or store your financial data.
How does the compound interest calculator help with FIRE planning?
Project the future value of your investments with the power of compound interest. See how regular contributions and time in the market can dramatically grow your wealth. This calculator helps you make data-driven decisions about your financial independence journey instead of relying on guesswork.