How to Use
- Enter an initial balance, such as 1,000.
- Add a recurring contribution, such as 100 per month.
- Choose contribution frequency, compound frequency, APY, and investment years.
- Review final balance, total contributions, total interest, and the growth chart.
- Click "Load Example" to inspect a 10-year monthly investing scenario.
Core Features
- Compound Growth Chart: ECharts visualizes principal, interest, and total balance over time.
- Flexible Contributions: Model monthly or annual recurring investments.
- Compound Frequency Control: Calculate with monthly, quarterly, or annual compounding.
- Private Local Math: Your financial inputs stay in the browser and are not uploaded.
- Instant Results: Change principal, contributions, APY, or years and the totals plus chart update immediately.
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Calculation Logic
The calculator advances the investment month by month. When a compounding period ends, earned interest is rolled into the balance; recurring contributions are added at the end of their selected period.
The basic idea is interest on interest: each compounding period multiplies the current balance by the period rate. The period rate comes from the annual return divided by the number of compounding periods per year.
Results are for educational planning only. They do not include inflation, taxes, exchange rates, platform fees, or financial advice.
FAQ
What is compound interest?
Compound interest means earned interest also earns future interest. The longer the timeline, the more visible the effect becomes.
How is this different from simple interest?
Simple interest only grows from the original principal. Compound interest reinvests previous interest into the next calculation period.
Are my financial numbers safe here?
Yes. Calculations run locally in your browser and do not upload your balance, contribution plan, or return assumptions.
Does this factor in inflation or taxes?
No. This version estimates gross growth before inflation, taxes, exchange rates, and fees, which makes it useful for baseline scenario comparison.