ScienForge

Retirement savings calculator

Project how a starting balance and regular contributions grow over time at a given rate of return, for retirement or any long-term goal.

Projected balance at retirement
691,150.47
Total contributed190,000.00
Growth from returns501,150.47
From current savings growing alone81,164.97
From future contributions609,985.50

Ignores taxes, fees, inflation and any employer match. A real 7% return above inflation is a common long-run planning assumption for a diversified stock portfolio, not a guarantee.

Retirement savings grow from two separate sources: the return earned on money already saved, and new contributions added regularly, which then also start earning returns of their own. Both compound over time, but they compound differently — a lump sum grows on its own, while a stream of contributions grows as an annuity.

Future value of current savings: FV = P(1 + r)ⁿ Future value of contributions: FV = C × [(1 + r)ⁿ − 1] / r

Why starting early dominates everything else

Time in the market compounding is the single biggest lever in this calculation, larger than the contribution amount for most realistic scenarios. Someone who invests $300/month for 40 years at 7% ends up with more than someone who invests $600/month for 20 years at the same rate — despite contributing the same total amount — because the first saver’s early contributions had decades longer to compound. This is the practical argument for starting retirement savings as early as possible, even with small amounts.

The 7% assumption, and why it is not guaranteed

7% is a commonly used long-run average for a diversified stock portfolio after adjusting for inflation, based on historical US market returns over many decades. It says nothing about any specific year or even decade — markets can and do decline for extended periods, and sequence-of-returns risk (a downturn early or late in your saving/withdrawal timeline) can significantly affect outcomes even when the long-run average holds. Treat any single number here as a planning estimate, not a forecast.

What is missing from this projection

  • Employer matching. If your employer matches contributions to a 401(k) or similar plan, that match is essentially free money that should be added to your monthly contribution figure before running the numbers — leaving it out understates your real trajectory substantially.
  • Taxes. Traditional retirement accounts defer tax until withdrawal; Roth accounts tax contributions now but not withdrawals. The effective amount you actually get to spend differs between the two even at an identical account balance.
  • Fees. Fund expense ratios and account fees compound negatively the same way returns compound positively — a 1% annual fee on a 40-year timeline meaningfully erodes the final balance, more than the flat 1% suggests.
  • Inflation. If the 7% figure is already inflation-adjusted (a real return), the projected balance is in today’s purchasing power. If it is a nominal return instead, the actual purchasing power at retirement will be lower than the dollar figure suggests.

Related calculators