How it works

Compound interest is the idea that your balance can grow on itself over time: you earn returns on your original deposit and on the returns you’ve already earned. When you add monthly contributions, you’re feeding the compounding engine continuously.

1. Enter starting amount and monthly contribution.
2. Enter an estimated annual return and time horizon.
3. The calculator estimates future value with compounding.

Use this for planning and “what-if” scenarios: try changing time, contributions, or return rate to see which lever has the biggest effect.

Formula

Example

How to interpret your result

Common mistakes

• Assuming the projection is guaranteed (returns vary year to year).
• Ignoring inflation when planning decades ahead.
• Over-focusing on rate and under-focusing on consistency of contributions.
• Using a return assumption that includes high-risk outcomes without acknowledging uncertainty.

Comparison table