Compound Interest on $100 at 8% for 40 Years
Calculate how just $100 grows at 8% annual interest compounded monthly over 40 years.
How to use this tool
- Enter starting amount, annual interest rate, compounding frequency and years in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your final balance and the full breakdown beneath it.
Even a small amount grows substantially over 40 years; this example illustrates the power of starting early.
Frequently asked questions
- What does compounding frequency change?
- More frequent compounding (e.g. daily vs annually) earns slightly more, because interest is added — and starts earning — sooner.
- Does this include monthly contributions?
- No — this is for a single lump sum. Use the Investment Growth Calculator to add regular monthly contributions.