Calculator
Investment return calculator
Combine a starting balance with monthly contributions and see how they grow over time. Compare different rates and horizons in seconds.
Updated July 2026
$
$
%
Future value
$691,150
Total contributed
$190,000
Investment growth
$501,150
How it works
FV = P × (1 + r/12)^(12t) + PMT × [((1 + r/12)^(12t) − 1) / (r/12)]
- P is your starting balance.
- PMT is your monthly contribution.
- r is the annual return as a decimal.
- t is the number of years.
- Compounds monthly — a reasonable proxy for most brokerage accounts.
Worked examples
- $10,000 start + $500/month at 7% for 30 years = ~$690,000.
- Doubling the monthly contribution nearly doubles the final balance over long horizons.
- Time matters most — starting 5 years earlier often beats saving 25% more per month.
Frequently asked questions
What return should I use?
Long-term US stocks have averaged about 10% nominal, roughly 7% real (after inflation). Balanced portfolios produce lower expected returns with lower volatility. Being conservative reduces the risk of over-optimism.
Is this a promise?
No — it's a projection based on your inputs. Actual returns vary year to year; the calculator smooths that into an average.
How is this different from compound interest?
Same underlying math. This calculator lets you combine a starting balance with monthly contributions in one view.
Related
Educational information only. Not personalised financial advice. Consult a qualified professional for decisions specific to your situation.