Simple vs Compound Interest: $100 at 12% for 40 Years
At 12% for 40 years, compound interest grows $100 to roughly $9,305 while simple interest yields only $580.
How to use this tool
- Enter principal, annual interest rate and years in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your compound balance and the full breakdown beneath it.
Over 40 years at 12%, compound interest grows $100 by almost 100x — versus less than 7x with simple interest.
Frequently asked questions
- When do simple and compound give the same result?
- At t = 1 year (with annual compounding) they are identical. Beyond year 1 compound interest always exceeds simple interest for positive rates.
- Which does a bank savings account use?
- Most savings accounts and mortgages use compound interest. Some short-term loans and bonds use simple interest.