How to use this calculator
- Enter your initial amount — the lump sum you already have invested. Use 0 if you're starting from scratch.
- Enter your monthly contribution and expected annual return. Interest compounds monthly.
- Set the number of years — results, chart, and the yearly table update as you type.
The formula
FV = P×(1+i)^n + PMT×[((1+i)^n − 1) / i]
P = initial amount, PMT = monthly contribution, i = monthly rate (annual ÷ 12), n = total months. Contributions are treated as end-of-month deposits.
Frequently asked questions
What is compound interest?
Compound interest means your earned interest itself earns interest: each period's gains are added to the principal and keep growing. Over long horizons compounding dramatically outperforms simple interest.
When are contributions added?
Contributions are treated as end-of-month deposits that start earning the following month — the most common convention. Beginning-of-month deposits would produce a slightly higher final value.
What return should I enter?
Use a conservative estimate based on your actual investments — for example, broad index funds have historically returned roughly 5–8% annually. Enter 0 to see pure principal accumulation.
Are taxes and fees included?
No. Results are gross of taxes and fees. Your real take-home amount will be lower after taxes, costs, and inflation.
Disclaimer Results are for reference only and do not constitute financial, tax, or legal advice. Actual rates, returns, and fees depend on the terms of your financial institution.