Total Contributions
13,000,000
Interest Earned
10,264,324
Growth Over Time
11020 years
ContributionsInterest
Compound Interest Formula
A = P(1 + r/n)^(nt)
A = final amount, P = principal, r = annual rate, n = compounds per year, t = years. Compound interest earns interest on both the initial principal and accumulated interest.
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What is Compound Interest?
Compound interest is interest earned not only on your original principal but also on the interest you have already accumulated. Because interest earns interest, your balance grows faster and faster over time — an effect often called the snowball of compounding and famously described as one of the most powerful forces in finance. This calculator models an initial deposit, an annual rate, a number of years, how often interest compounds, and optional monthly contributions, then visualizes your future balance year by year. Whether you are saving in a retirement account, an index fund, or a high-yield savings account, understanding compounding is the foundation of long-term wealth building, and seeing the growth curve makes the value of starting early strikingly clear.
How to Use
1. Enter your initial investment (the principal).
2. Enter the expected annual interest rate (%).
3. Enter the number of years you plan to invest.
4. Choose how often interest compounds per year (monthly = 12, annually = 1, etc.).
5. Add a monthly contribution if you plan to invest regularly.
The result shows your final balance, total contributions, and interest earned, plus the year-by-year progression.
Formula & Definition
Without contributions, the core compound interest formula is:
A = P × (1 + r ÷ n)^(n × t)
where A is the final amount, P is the principal, r is the annual rate (as a decimal), n is the number of compounding periods per year, and t is the number of years. For example, $10,000 at 5% compounded annually for 20 years grows to 10,000 × (1.05)^20 ≈ $26,533. With monthly contributions, the calculator repeats the compounding each period while adding the new deposits. A higher compounding frequency n yields a slightly larger final amount for the same rate.
Interpreting Results
In your final balance, 'total contributions' is the money you put in, while 'interest' is the growth your money generated. The longer the horizon, the larger the interest portion becomes, which is the heart of compounding. Keep in mind that the annual rate is an assumption, not a guarantee — investments can lose value, and past returns do not predict the future. This calculation also ignores taxes, fees, and inflation. Real take-home returns are reduced by taxes on gains (many countries offer tax-advantaged accounts) and by fund expense ratios, while inflation erodes the future purchasing power of your balance, so it is wise to think in terms of real, inflation-adjusted returns.
Frequently Asked Questions
How is compound interest different from simple interest? ▾
Simple interest is earned only on the original principal, while compound interest is earned on principal plus accumulated interest. Over long periods the gap between them becomes very large.
How can I maximize compounding? ▾
Start as early as possible, stay invested for the long term, and reinvest your returns rather than withdrawing them. Time is the most powerful ingredient.
What rate should I use? ▾
There is no guaranteed number. Use current savings rates for deposits or historical average returns for investments, and try several scenarios to see a realistic range.
Does this include taxes and fees? ▾
No. The calculation excludes taxes, fees, and inflation. Real net returns are lower, so estimate conservatively and factor in your local tax rules.
This tool provides general projections only and is not financial advice or a guarantee of investment results. Investments carry the risk of loss. Consult a qualified professional before making important decisions.