Retirement savings calculator

The calculator walks you through five inputs, wizard-style:

1. Current age: your age today, from 18 to 80. 2. Retirement age: when you plan to stop working. The default is 67, the full Social Security retirement age for Americans born in 1960 or later. Planning to retire early? Lower it and watch the balance shrink — time is the biggest lever. 3. Current savings: everything already earmarked for retirement: 401(k), traditional or Roth IRA, brokerage accounts. 4. Monthly contribution: what you will add every month going forward. Enter 0 to see how your existing savings grow on their own. 5. Expected annual return (%): the average yearly return you expect. Planners often model 6-8% nominal for a stock-heavy portfolio and 4-5% for a balanced one.

You get three results: the balance at retirement (what you will have at your chosen age), the total contributed (current savings plus every future monthly deposit) and the investment growth (the gap between the two — the part compound interest earns for you). Interest compounds monthly and contributions are credited at the end of each month, the standard convention for recurring savings plans.

The calculator uses the standard future-value formula from financial mathematics: a lump sum compounding monthly plus an ordinary annuity of recurring contributions (credited at the end of each month).

In plain text:

Balance = S × (1 + r)^n + A × ((1 + r)^n − 1) / r

where:

• S = current savings
• A = monthly contribution
• r = annual return / 100 / 12 (the monthly rate)
• n = years until retirement × 12 (the number of months)

If the return is 0%, the formula collapses to Balance = S + A × n. Total contributed is S + A × n, and investment growth is the final balance minus the total contributed.

Worked example: age 30, retiring at 67, $15,000 saved, $400 a month at 6% per year.

• n = (67 − 30) × 12 = 444 months
• r = 6 / 100 / 12 = 0.005
• (1 + r)^444 = 9.156540
• Lump-sum part: 15,000 × 9.156540 = $137,348.10
• Contributions part: 400 × (9.156540 − 1) / 0.005 = $652,523.25
• Balance at 67: $789,871.35
• Total contributed: 15,000 + 400 × 444 = $192,600
• Investment growth: 789,871.35 − 192,600 = $597,271.35

More than 75 cents of every dollar in that final balance comes from compounding, not from the saver's paycheck — that is what 37 years of monthly compounding does.

Three typical U.S. saver profiles, all retiring at 67, with more conservative returns as the horizon shortens:

Two lessons jump out of the table. First: time beats money. The 25-year-old contributes the least in total ($161,200) yet retires a millionaire, because every dollar gets up to 42 years to compound. Second: starting late is fixed with bigger contributions, not riskier bets. The 45-year-old already puts in $800 a month — nearly triple the youngest saver — and still ends up with roughly half the balance. Chasing higher returns to close that gap adds sequence risk exactly when a portfolio can least afford a crash, which is why target-date funds shift toward bonds as retirement approaches.

U.S. retirement planning rests on three legs: Social Security, employer plans like the 401(k), and personal savings in IRAs or taxable accounts. Social Security replaces only about 40% of the average earner's pre-retirement income, while most planners suggest you will need 70-80% to maintain your lifestyle — the gap is yours to fill. The usual priority order is: contribute enough to capture the full employer 401(k) match (it is an instant 50-100% return), then fund an IRA or Roth IRA, then go back to the 401(k) up to the IRS annual limit, which is adjusted every year. A common rule of thumb is to save 10-15% of gross income for retirement, and the 4% rule offers a rough drawdown estimate: a $1 million portfolio supports about $40,000 of first-year withdrawals.

Keep the calculator's limits in mind: results are in nominal dollars (inflation is not subtracted), taxes and fund fees are excluded, and the return is assumed constant while real markets swing widely year to year. To think in today's purchasing power, enter a real return — your expected return minus roughly 2-3% inflation.

Important notice: this calculator is an educational tool, not financial advice or an investment recommendation. Past performance does not guarantee future results. For decisions about your retirement, consult a qualified financial advisor.

For most Americans, Social Security replaces only around 40% of pre-retirement income, so what you build in your 401(k), IRA or brokerage account does the heavy lifting. This calculator estimates the nest egg you will have at your chosen retirement age, combining what you have saved so far with your monthly contributions and an expected annual return. For example: at age 35 with $25,000 already saved and $500 a month earning an average 6% per year, you would reach 67 with $748,550.57 — and $531,550.57 of that would be investment growth, not money out of your own pocket. Enter your numbers to see whether you are on track, then adjust the monthly contribution or the retirement age until the final balance matches the retirement you actually want.