Watch Your Money Grow Over Time
Calculate how your investment grows with compound interest. Adjust principal, rate, and compounding frequency to see the power of compounding.
⚙Calculator Inputs
The initial amount you're investing
Expected annual return rate
How long you plan to invest
How often interest is compounded
Quick Presets
Final Value
$22,196.40
Interest Earned
$12,196.40
Principal
$10,000.00
Growth Multiple
2.22×
Growth Over Time
What is Compound Interest?
Compound interest is the process of earning interest on both your initial principal and the interest already accumulated. Unlike simple interest — which is calculated only on the principal — compound interest grows exponentially over time. Albert Einstein reportedly called it the "eighth wonder of the world."
For example, $10,000 invested at 8% annual interest compounded monthly grows to $22,196 after 10 years — more than double your initial investment, with $12,196 earned purely from compounding.
The Compound Interest Formula
Compounding Frequency Comparison
The frequency at which interest compounds significantly affects your final balance. Here's how $10,000 at 8% grows over 10 years with different compounding frequencies:
| Frequency | Times/Year | Final Value | Interest Earned |
|---|---|---|---|
| Annually | 1 | $21,589 | $11,589 |
| Quarterly | 4 | $22,080 | $12,080 |
| Monthly | 12 | $22,196 | $12,196 |
| Daily | 365 | $22,253 | $12,253 |
Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. It grows exponentially over time, making it the most powerful force in long-term investing.
What is the compound interest formula?
A = P × (1 + r/n)^(n×t), where A is the final amount, P is the principal, r is the annual interest rate, n is the compounding frequency per year, and t is the time in years.
How often should interest compound for best results?
More frequent compounding yields slightly higher returns. Daily compounding produces the most growth, followed by monthly, quarterly, and annual compounding.
What is a good compound interest rate?
Historically, the S&P 500 has averaged around 10% annually. High-yield savings accounts offer 4–5%. Bonds typically yield 3–6%. The "best" rate depends on your risk tolerance.
How long does it take to double money with compound interest?
Use the Rule of 72: divide 72 by your annual interest rate. At 8%, your money doubles in approximately 9 years (72 ÷ 8 = 9).
What is the difference between compound and simple interest?
Simple interest is calculated only on the principal. Compound interest is calculated on the principal plus accumulated interest, resulting in exponentially higher returns over time.