How 401k Compounding Works
Your balance grows on two engines at once: market compounding on everything already invested, plus fresh fuel each year from your contributions and your employer's match. The match is a guaranteed instant return, 50% match means every $1,000 you contribute instantly becomes $1,500 before markets even move. Over decades, employer dollars and their compounding often contribute six figures most savers never notice.
Balance(t+1) = Balance(t) × (1+r) + Employee + Employer match
r = Annual Return · Employer annual = min(Contribution × Match%, Cap)
Worked Example
Scenario: $50k now + $12k/yr + 50% match to $6k cap at 7% for 25 years
Future Value
~$1.1M
You Contributed
$300,000
Employer Added
$150,000
Pure Growth
~$650,000
The match alone plus its compounding covers years of retirement spending, never leave it unclaimed.
What the Calculator Shows
- Future value, projected balance at retirement
- Your contributions, total out-of-pocket deposits
- Employer contributions, free money captured via match
- Investment growth, compounding gains above all deposits
- Yearly table, balance trajectory for every year
Retirement Planning Tips
Contribute at least enough for the full match before any other investing. The 4% rule suggests ~25× annual spending as a target, $60k/yr spending → ~$1.5M. Model tax strategy with our Roth Conversion Calculator and timelines with our FIRE Calculator.