Investment Calculator
Calculate compound interest growth.
About this tool
The Investment Calculator projects how a lump-sum investment grows over time at a given annual rate of return, with optional monthly contributions. It visualises the power of compound growth so you can model different saving strategies.
How it works
- Enter your initial investment (principal).
- Enter the expected annual return percentage.
- Enter the investment period in years.
- Optionally, add monthly contributions to model regular saving.
- Review the projected final value and total interest earned.
Example use cases
- Retirement saving: $500/month for 30 years at 7% annual return grows to approximately $566,000 - with only $180,000 contributed.
- Lump-sum investment: A $10,000 one-time investment at 8% annual return for 20 years grows to approximately $46,600.
Frequently asked questions
What annual return rate should I use?
The S&P 500 has historically averaged around 10% before inflation. A conservative planning assumption is 6-7% after accounting for inflation and fees.
Does the calculator account for inflation?
No - it shows nominal growth. To estimate real purchasing power, use a return rate 2-3% lower than your nominal expected return.