1. What does this tool do
This free online compound interest calculator shows how your savings or investments grow with compounding. Use it as a savings calculator or investment growth calculator to plan retirement, compare rates, or teach compound growth. Set an initial amount, optional regular contributions, and compounding frequency—see the result over time. Free and private; no sign-up, all in your browser. Ideal for savings accounts, CDs, or modeling growth with contributions.
2. How to use it
Quick start: Enter initial amount, interest rate, compounding frequency (e.g. monthly), and term. Optionally add regular contributions. View projected balance and growth—then tweak inputs to compare scenarios.
- Enter initial amount — The sum you start with (or 0 if you only add regularly).
- Set interest rate — Annual (or periodic) rate in percent.
- Add contributions (optional) — Regular deposit amount and frequency (e.g. monthly).
- Choose compounding — How often interest compounds (e.g. monthly, quarterly, annually).
- Set term — Number of years (or periods). View the projected balance and growth.
3. How it works
Future value is calculated with the compound interest formula; with regular contributions, each contribution is compounded for the remaining periods. The tool may show a year-by-year or period-by-period breakdown. All calculations run in your browser; no data is sent to any server.
4. Use cases & examples
- Savings calculator — See how a savings account or CD grows with monthly or annual compounding.
- Retirement planning — Model growth of a lump sum plus monthly contributions.
- Compare rates — Try different APYs to see the impact on final balance.
- Education — Explain compound growth with concrete numbers.
Example
- $10,000 at 5% annual, compounded monthly, 10 years → ~$16,470 (approximate; use the tool for exact).
- Add $100/month: balance grows faster; the tool shows the combined effect.
5. Limitations & known constraints
- Assumptions — Assumes constant rate and consistent contributions; real accounts may have variable rates or fees.
- No tax — Results are before tax; tax-deferred or taxable accounts need separate consideration.
- Inflation — The result is nominal growth; inflation is not deducted.