Retirement planning is two questions in one: how much will I have, and how much is enough? This calculator simulates both month by month — your savings growing until retirement, then shrinking as you draw the income you want — and tells you plainly whether the money lasts and what monthly amount would make it last.

Steps

1. 1 Enter your age today, the age you want to retire and the age the plan should cover — 90 is a common, cautious choice.
2. 2 Add what you have saved, what you save each month, the yearly raise in that amount and the returns you expect before and after retirement.
3. 3 Type the monthly income you want in today's money. The result shows your projected savings, the amount you actually need and the monthly saving that gets you there.

Why the target is in today's money

Nobody can picture what 2,500 a month buys in 35 years. You enter the income you would want today; the calculator raises it by the inflation rate every year until retirement and keeps raising it afterwards, so the withdrawals in the simulation keep their purchasing power. At 2% inflation, 2,500 today is about 5,000 in 35 years — which is why the needed nest egg looks large.

Needed savings versus projected savings

Projected savings come from compounding your contributions at the pre-retirement return. The needed amount is calculated backwards from the last month of the plan: what balance at retirement, growing at the retirement return, exactly funds the inflation-adjusted income until the end age. Because both numbers come from the same month-by-month arithmetic they are directly comparable; the gap between them is what the monthly saving needed closes.

The 4% rule

A common rule of thumb says you can withdraw 4% of your savings in the first year of retirement and raise it with inflation each year, with a good chance of the money lasting 30 years. The calculator shows what 4% of your projected savings means per month so you can compare it with the income you asked for. It is a sanity check, not a guarantee — lower returns or a longer retirement call for a lower rate.

Choosing the return rates

Use a long-run average, not a hopeful one: diversified stock-heavy portfolios have returned roughly 6–8% a year in nominal terms over decades, and most people shift to a more conservative mix in retirement, so the second rate should be lower, often 3–5%. Try a pessimistic pair as well; a plan that only works with optimistic numbers is not a plan.