This calculator is for informational purposes only and does not constitute financial advice. Results are estimates based on inputs you provide. Consult a qualified financial advisor before making financial decisions.
Retirement Planner
Visualize your 401k growth and plan for financial freedom.
S&P 500 average is ~10%
Historical average is ~3%
Total Savings (65)
$523,369
Total Interest
$293,369
Wealth Growth Projection
The Power of Time
Notice how the "Total Balance" curve (purple) starts to separate exponentially from "Your Contributions" (green) over time? That is compound interest working for you. Starting just 5 years earlier can double your retirement nest egg!
This calculator projects what your retirement savings could grow to by compounding your current balance and monthly contributions at a steady real rate of return. It is a single-path projection: useful for seeing how much the start age, contribution and return assumptions matter, not a forecast of what markets will do.
How the projection is calculated
The real annual return is (1 + expected return) ÷ (1 + inflation) − 1, so a 7% return with 3% inflation grows money at about 3.9% a year in today's dollars. Each month the balance earns one twelfth of that rate and your contribution is added, from your current age to the retirement age you set. The chart separates what you put in from what compounding added.
When to use this calculator
Use it to compare scenarios rather than to get one number: move the retirement age by five years, or the contribution by $200 a month, and watch how much the end balance changes. Pair it with the FIRE calculator if you want to know what size of balance supports a given level of spending, and with the debt payoff planner if high-interest debt is competing for the same monthly money.
Worked example
A 40-year-old with $200,000 saved, contributing $1,500 a month until 65 at a 7% expected return and 3% inflation (a real rate of about 3.88%), ends with roughly $1,290,000 in today's dollars. About $650,000 of that is money put in and the rest is growth, which is why the curve bends upward in the final decade.
Limits and assumptions
The projection is deterministic. It compounds your current balance and monthly contributions at a single real rate of return, derived from the nominal return and inflation inputs as (1 + return) ÷ (1 + inflation) − 1, from your current age to the retirement age you choose. It does not run randomised market scenarios, so it shows one path rather than a range of outcomes, and a year with a crash looks the same as any other. Yearly balances, contributions and interest are rounded to whole dollars.
Taxes, fund fees, employer matching, Social Security or pension income and the drawdown phase after retirement are outside the model: the result is the balance on the day you retire, not how long that balance would last.
Frequently asked questions
Does this calculator run a Monte Carlo simulation?
No. It compounds your balance and contributions at one steady real rate of return, so it shows a single path. A Monte Carlo tool runs thousands of scenarios with randomised returns and reports a probability of success instead of one number. Use this calculator to compare assumptions (start age, contribution, return); it cannot tell you the odds of a plan working.
How much do I need to retire?
A common rule is the 25× rule: save 25 times your annual expenses. That's the inverse of the 4% safe withdrawal rate. So if you spend $50,000/year, you need ~$1.25 million invested.
What is the 4% rule?
The 4% rule says you can withdraw 4% of your portfolio in your first year of retirement and adjust for inflation each year, with a high probability of not running out over 30 years. It's a starting point, not a guarantee.
Should I include Social Security in my retirement plan?
Yes, but this calculator has no field for it. Estimate your expected benefit separately (the Social Security Administration publishes a statement for your record) and treat the portfolio as only needing to cover the spending above that benefit.
Guides for this calculator
- Monte Carlo Retirement Calculator: What Your Odds Mean (2026)
A Monte Carlo retirement calculator runs 1,000+ simulated markets against your plan and scores it. Here is what the success rate means and how to act on it.
- How Much Money Do I Actually Need to Save for Retirement? (2026 Guide)
Forget the guesswork. Learn how to use the Rule of 25, age-based salary benchmarks, and withdrawal rates to calculate your exact retirement savings target.