Compound Interest Calculator
This is a simplified estimate assuming a constant rate. It ignores taxes, fees and inflation and is not financial advice.
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See how your money can grow with compound interest. Enter an initial amount, an interest rate, a time span and an optional monthly contribution to get the future value, total interest earned and a year-by-year breakdown. This is an estimate for learning, not financial advice, and runs entirely in your browser.
How to use
- Enter your initial amount, annual rate and number of years.
- Choose how often interest compounds and add a monthly contribution if you like.
- Read the future value, interest earned and the growth chart.
How it works
Compound interest means you earn interest on your interest, not just on the original amount. The balance follows FV = P(1 + r/n)^(nt), where P is the principal, r the annual rate, n how many times a year it compounds, and t the years. Monthly contributions are added over time and then earn interest too, which is why regular investing grows so much over long periods.
Features
Compounding + contributions
Combine a starting amount with regular monthly contributions.
Compounding frequency
Compare yearly, quarterly, monthly or daily compounding.
Year-by-year breakdown
A chart shows how the balance builds up each year.
Interest vs contributions
See how much of the total is your money versus earned interest.
When to use it
Retirement planning
Estimate how a long-term savings habit could grow by retirement.
Regular investing
See the effect of investing a fixed amount every month.
Savings goals
Work out whether your plan reaches a target amount in time.
Compare scenarios
Try different rates and contributions to compare outcomes.
Notes
- Results assume a constant rate and contributions made each period.
- Taxes, fees and inflation are not included.
- Real investment returns vary and are never guaranteed.
- All calculation runs on your device; nothing is uploaded.
Not financial advice
This calculator is for general information and education only. It is a simplified estimate and not investment or financial advice. Consult a qualified financial professional before making decisions.
FAQ
- What is compound interest?
- It is interest calculated on both your original amount and the interest already earned, so your balance grows faster over time than with simple interest.
- Does compounding frequency matter?
- Yes, but modestly. More frequent compounding (daily vs yearly) gives a slightly higher result for the same rate.
- Are monthly contributions included?
- Yes. Contributions are added over time and then earn interest too, which is shown separately from your deposits.
- Does it account for taxes?
- No. This is a simplified estimate that ignores taxes, fees and inflation, so real results will differ.
- Is my data sent to a server?
- No. The calculation happens entirely in your browser and nothing is uploaded.