Retirement Calculator
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Retirement math is just two forces — what you put in and what growth does with it — stretched over decades. This calculator projects your nest egg at retirement age, splits it into contributions versus growth, and translates the total into monthly income using the 4% rule. Every number updates as you type.
How to use this retirement calculator
Five inputs, all straightforward:
- Your age now and retire at age: set the time horizon. Defaults: 35 now, 65 at retirement — 30 years of compounding.
- Current retirement savings ($): what's already invested. Defaults to $50,000.
- Monthly contribution ($): what you add each month, at the end of the month. Defaults to $800.
- Expected annual return (%): a constant yearly growth rate. Defaults to 7% — a middle-of-the-road planning assumption for a stock-heavy portfolio, not a prediction.
The headline is your projected nest egg. Below it: total contributions, how much growth contributed, and the 4% rule translated into monthly and annual retirement income.
Worked examples
Example 1 — the steady saver: You're 35 with $50,000 saved, adding $800 a month at 7% until 65. The nest egg reaches about $1,381,802. Of that, only $338,000 is money you put in — the remaining $1,043,802 is growth. The 4% rule turns it into roughly $4,606 a month of retirement income in year one. Three-quarters of the final number was earned by time, not by you.
Example 2 — starting ten years late: Same saver, but starting at 45 instead of 35 (20 years instead of 30). The nest egg is about $618,678 — less than half — with $242,000 contributed and $376,678 of growth, worth about $2,062 a month under the 4% rule. Those first ten years were the most valuable ones: money invested at 35 compounds for a full decade before the 45-year-old even starts.
Example 3 — doubling the contribution: Back to starting at 35, but $1,600 a month instead of $800. The nest egg jumps to about $2,357,778 — roughly $7,859 a month under the 4% rule. Contributions doubled, but the outcome grew by less than double, because the original $50,000 head start contributes the same in both cases. Early money matters more than extra money.
How the math works
The projection uses the future value of a lump sum plus the future value of a monthly annuity, with contributions at the end of each month:
Nest egg = initial × (1 + r)n + monthly × (((1 + r)n − 1) / r)
where r is the monthly return (annual ÷ 12) and n is the number of months. "Total contributions" is simply initial + monthly × months; "growth" is the nest egg minus that. The 4% rule income is nest egg × 0.04 ÷ 12 per month. Our methodology page documents the conventions behind every SialTV Money calculator.
Common mistakes and tips
- Assuming the return is guaranteed. 7% every year is a modeling shortcut — real markets deliver it in lumps, with down years mixed in. Run the calculator at 5% too; if the plan only works at 9%, the plan is fragile.
- Forgetting inflation. These are nominal dollars. At 3% inflation, $1,381,802 in 30 years buys what about $569,000 buys today. Think of the 4% income in today's purchasing power, not the sticker number.
- Ignoring fees. A 1% annual fee on a 7% gross return leaves you ~6% — over 30 years that haircut costs about a fifth of the ending balance. Fees compound against you exactly like returns compound for you.
- Counting the 4% rule as a promise. It's a planning heuristic from 1990s research on 30-year retirements, not a withdrawal contract. Bad early-retirement markets can still break it; flexibility (spending less after down years) is the real safety margin.
- Leaving the employer match on the table. A 401(k) match is an instant 50–100% return on matched dollars — nothing in the market competes. Capture the full match before raising contributions anywhere else.
- Treating "retirement age" as fixed. Two extra working years do double duty: two more years of contributions and two fewer years of withdrawals. The calculator shows the payoff instantly — try 67 instead of 65.
Frequently asked questions
How much do I need to retire?
A common starting point is 25 times your annual spending — the flip side of the 4% rule. Spend $80,000 a year and the rule suggests a $2,000,000 nest egg. It's a rule of thumb for planning, not a promise: your health, housing, and how flexible your spending is all move the real number.
What is the 4% rule?
It suggests you can withdraw 4% of your portfolio in the first year of retirement, then adjust that amount for inflation each year after, with the money lasting about 30 years. On a $1,381,802 nest egg that's about $4,606 a month in year one. It assumes a mix of stocks and bonds and average market behavior — not a guarantee.
What return should I assume?
Be conservative. US stocks have averaged roughly 10% a year before inflation over very long periods, but planners often model 6–8% nominal (4–6% after inflation) for a mixed portfolio. This calculator uses whatever you type — try 5%, 7%, and 9% to see how sensitive the answer is.
Is it too late to start at 40 or 50?
Starting later means less compounding, but the contributions still matter enormously. In our worked example, starting at 45 instead of 35 cuts the nest egg from about $1,381,802 to about $618,678 — yet $376,678 of that is still growth. The worst time to start was decades ago; the second-best time is this month.
Should I count on Social Security too?
Yes — treat it as a supplement, not the foundation. The calculator shows what your own savings produce; add your estimated Social Security benefit on top when judging whether the total covers your spending. The SSA's own statements stress benefits are designed to replace only part of pre-retirement income.
Do contributions go in at the start or end of the month?
This calculator adds each monthly contribution at the end of the month, the same convention as our investment calculator — the conservative choice, since money contributed later earns slightly less. The difference versus beginning-of-month is small over decades.