What this tool does
Project a retirement balance from a starting amount, fixed end-of-month contributions, time and an assumed constant annual return.
How to use it
- Enter the balance already saved and the monthly contribution.
- Enter years until retirement and an assumed annual return.
- Calculate several scenarios rather than treating one return assumption as a forecast.
Formula and method
The annual return is divided by 12. Each month the existing balance grows by that rate, then the contribution is added at month-end. Contributions equal starting balance plus monthly amount×months; projected growth is the result minus contributions.
Worked example
Starting with $10,000 and adding $500 monthly for 20 years at 6% produces a projected balance above $250,000. Direct contributions total $130,000; the rest is modeled growth.
Common uses
- Testing contribution changes
- Comparing time horizons
- Separating deposits from modeled growth
Limitations
Returns are not constant or guaranteed. The model omits taxes, fees, inflation, contribution timing differences, withdrawals and market volatility. Use real account costs and conservative ranges; retirement planning may require a qualified professional.
FAQ
Are contributions made at the start or end of the month?
The calculator adds them at the end of each modeled month, after that month’s return.
Is the result in today’s money?
No. It is nominal unless you separately choose a return already adjusted for inflation.