Retirement Calculator
Project your retirement savings and the monthly income they could support.
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Compound Interest Calculator
See what a starting amount plus steady monthly contributions grows into — and how much of the final value is pure compounding.
Your numbers
Results
Calculated entirely on your device — never transmitted or stored.
View mathematical formula & assumptions
Future value with regular contributions, compounded monthly:
FV = P × (1 + r)n + PMT × [((1 + r)n − 1) / r]
FV — future value (the result shown above)
P — starting amount
PMT — monthly contribution
r — monthly interest rate (annual rate ÷ 12)
n — total number of months (years × 12)
How this calculator works
Compound interest means your returns start earning returns of their own. Each month, the calculator applies one month of growth to your balance, then adds your contribution. Repeated over years, that loop produces the famous "hockey stick" curve — slow at first, then accelerating as the interest-on-interest snowball gets rolling.
The three levers
- Time — the most powerful lever. Money invested in your 20s can outgrow much larger amounts invested in your 40s.
- Contributions — steady monthly investing builds the base that compounding multiplies.
- Rate of return — a 7% long-term average roughly doubles money every 10 years; small rate differences compound into large gaps.
Choosing a realistic rate
The U.S. stock market has historically averaged roughly 7–10% per year over long periods, before inflation — but with big swings year to year. High-yield savings accounts currently pay far less but with no volatility. Try a conservative and an optimistic rate to see the realistic range for your plan, and remember that investment fees come directly out of your return.