401k Growth Calculator

About this calculator

A 401(k) balance grows from three compounding sources: your existing balance, your ongoing contributions (a percentage of salary deducted each pay period), and the employer match — commonly structured as something like “100% match on the first 3% of salary, 50% on the next 2%” — all invested and compounded at an assumed annual rate of return, typically modeled around 6-8% for a diversified stock/bond portfolio over the long term.

Employees planning retirement savings use this projection to see the real cost of leaving free money on the table — under-contributing below the match threshold effectively forfeits part of your compensation — and to understand how much of their eventual balance comes from their own contributions versus employer match versus investment growth compounding over decades, since even small early increases in contribution rate compound into large differences by retirement age.

This calculator takes your current balance, salary, contribution rate, employer match and expected return, and projects your 401(k) balance forward year by year.