Loan and mortgage calculators show a balance shrinking to zero — this tool shows the opposite: how a savings or investment balance grows when interest compounds and you keep adding to it. Seeing the year-by-year numbers makes compounding’s long-term effect obvious in a way a single final number never does.
What Is the Compound Interest Calculator?
Enter a starting amount, an annual interest rate, a time horizon, and an optional monthly contribution, and the tool projects your balance year by year — separating how much came from your own contributions versus how much came purely from compounding interest. Choose monthly, quarterly, annual, or daily compounding to match your actual account terms.
How to Use It
- Open the tool at /tools/compound-interest-calculator.
- Enter your initial amount, annual rate, number of years, and monthly contribution.
- Pick the compounding frequency that matches your account (most savings and investment accounts compound monthly).
- Review the final balance, total contributed, and total interest earned.
- Scroll the year-by-year table to see exactly how the balance grows over time.
Key Features
- Year-by-year growth table, not just a single final number.
- Optional monthly contributions, distributed proportionally across your chosen compounding frequency.
- Four compounding frequency options — monthly, quarterly, annual, daily.
- Clear separation of contributed money vs. earned interest, showing exactly how much compounding actually added.
When to Use This Tool
- Planning retirement or long-term savings contributions and seeing the projected outcome.
- Comparing the effect of starting earlier vs. contributing more later.
- Understanding how compounding frequency affects growth at a given nominal rate.
Try It Now
Open Compound Interest Calculator directly, or press ⌘K and type the tool name from anywhere on the site.
Part of the Math & Numbers collection on WebdevToolbox — free, browser-based developer tools with no login required.