Compound Interest Calc

Key features

• Models an initial principal, monthly contributions, an annual rate (0–100%) and a horizon of 1–50 years.
• Four compounding frequencies — monthly, quarterly, annually and daily — converted to an exact-equivalent monthly rate, with the effective annual rate (EAR) shown.
• Contributions are added at the end of each month (the ordinary annuity convention).
• The big three numbers: final balance, total deposited and interest earned, with a growth-percentage badge.
• A chart plotting balance against deposits — the widening gap between the lines is your interest.
• A scrollable year-by-year table showing deposited, interest and balance at every year-end.

How it works

1. 1

   Set the plan

   Enter a starting principal, a monthly contribution and the annual interest rate.

2. 2

   Choose the horizon and compounding

   Slide the years (1–50) and pick monthly, quarterly, annual or daily compounding.

3. 3

   Or start from a preset

   Chips load scenarios like “$1k + $100/mo @7%” so you can play immediately.

4. 4

   Read the results

   Final balance, deposited and interest tiles first, then the growth chart and the year-by-year table.

Tips for better results

• 💡Compare compounding frequencies on the same numbers — the EAR line shows exactly how much daily beats annual (usually a fraction of a percent).
• 💡On the chart, the dashed line is money you put in and the solid line is what you have; the gap between them is compounding at work.
• 💡Time matters more than rate at small balances — extend the years slider before chasing extra interest.
• 💡The simulation is pure maths: no fees, taxes or inflation. Real-world returns vary, and past rates don't guarantee future ones.

Frequently asked questions