How to Use the Compound Interest Calculator

A step-by-step guide to using the Compound Interest interactive visualizer.

Step-by-Step Guide

1. 1

   Set the principal P — the starting amount you invest or deposit.

2. 2

   Set the annual interest rate r as a percentage.

3. 3

   Choose how many times per year interest compounds (n=12 for monthly, 365 for daily).

4. 4

   Set the number of years t and watch the compound growth bars (green) tower over simple interest bars (indigo).

5. 5

   The 'extra' field in the result shows how much MORE you earn vs simple interest.

Formula Explanation

If you put money in a bank and the bank gives you free money every year on top of previous free money — it snowballs! After many years, the extra growth is enormous compared to if you only earned interest on the original amount.

Real-World Applications

• → Retirement funds use compound interest to project 40-year growth forecasts for pension planning.
• → Credit card debt compounds monthly — a $5,000 balance at 20% APR doubles in under 4 years.
• → Warren Buffett's wealth is almost entirely the result of compound interest applied over 60+ years.