Use it for contribution decisions
This is useful when you are deciding whether to increase contributions, chase the full employer match, or test a later retirement age. Switch the market scenario to stress-test the plan against real-world drawdowns.
RetirementCalculator
401(k) Calculator
Estimate how your 401(k) balance could grow based on contributions, employer match, and annual return.
What it means
About this calculator.
Future dollars vs today's dollars
Projections are first computed in nominal (future) dollars and then discounted to today's purchasing power using the inflation rate you supply. The chart shows future dollars to match how balances are actually quoted; the result cards labeled "today's dollars" tell you what those numbers actually buy.
Traditional vs Roth
Traditional 401(k) contributions are pre-tax and the entire balance is taxed at withdrawal. Roth 401(k) contributions are after-tax and the entire balance comes out tax-free. The retirement tax rate input only applies to Traditional withdrawals.
FAQ
Questions people usually have.
Does this account for IRS contribution limits?
No. It assumes your annual contribution is already realistic for your situation. The 2025 employee deferral limit is $23,500 ($31,000 if you're 50+); the projection scales your contribution up each year by the salary-growth rate, so set the starting number to what you'd actually contribute this year.
Why do contributions grow over time?
Most people get raises. The salary-growth rate scales both your annual contribution and the employer match each year, which is a much more accurate long-term picture than holding contributions flat for 30 years. Set salary growth to 0% if you want the old flat-contribution behavior.
How is inflation handled?
The chart and "Projected balance at retirement" show nominal future dollars. Everything labeled "today's dollars" divides that nominal value by (1 + inflation)^years, so $1M in 30 years at 2.5% inflation reads as about $477K in today's purchasing power. Inflation does not affect the underlying compounding; it only affects how we present the result.
How is the retirement tax handled?
Traditional 401(k) withdrawals are taxed as ordinary income. The calculator runs your 4% annual withdrawal through the 2025 federal brackets at single-filer status (the conservative default), then adds your state's 2025 income tax if you picked one. Roth balances skip both. This is a planning estimate, not a substitute for a CPA — actual tax depends on RMDs, Social Security, filing status, and the brackets in force at the time.
Why do the crashes hit at the end?
Because that's where they actually hurt. A 40% drawdown thirty years out barely moves your retirement number; the same drawdown three years out can rewrite your plans. The historical sequences (2008, dot-com, 1929, COVID) are placed in the final years before your retirement age to surface sequence-of-returns risk, which is the part most people underestimate.
What's Monte Carlo doing exactly?
1,000 simulated paths where each year's return is drawn from a normal distribution centered on your expected return with a 16% annualized standard deviation (roughly matching historical US equities). The low / median / high cards show the 10th, 50th, and 90th percentile final balances across all 1,000 paths.