Compound Interest Calculator
Start with an amount, add a regular monthly contribution, pick a rate, and this projects how it all grows — splitting your future balance into what you put in and what the interest earned. The math runs locally and is meant for planning, not as financial advice.
- 100% free
- Private & safe
- Runs in your browser
Read our complete guide: How Compound Interest Works: Formula, Examples & Wealth Strategies
Why use Compound Interest Calculator?
Compound Interest Calculator gives you accurate results instantly, with the underlying formula shown so you can trust the numbers.
- Runs instantly in your browser — nothing to install, nothing uploaded.
- Completely free, with no account, no watermarks and no usage limits.
- Handles FV = P(1+i)^N + PMT × ((1+i)^N − 1) ÷ i; i = annual rate ÷ 12, N = months.
- Enter your initial amount and monthly contribution.
- Works on any device — desktop, tablet and phone — and is fully keyboard accessible.
How to use Compound Interest Calculator
- Enter your initial amount and monthly contribution.
- Set the annual interest rate and number of years.
- See the projected future value and how much is interest.
- Adjust inputs to compare scenarios.
Examples
- $10,000 plus $200/month at 7% for 20 years.
- Comparing 5% vs 8% average returns.
Formulas
- FV = P(1+i)^N + PMT × ((1+i)^N − 1) ÷ i
- i = annual rate ÷ 12, N = months
Limitations
- Assumes a constant rate compounded monthly; real returns fluctuate.
- Ignores taxes, fees and inflation.
- Not financial advice.
Frequently asked questions
How often does it compound?
Monthly, matching the monthly contribution schedule.
Does it account for inflation or taxes?
No — results are nominal estimates before taxes, fees and inflation.
Is this financial advice?
No, it is an informational estimate only.
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