401(k) growth calculator

Project a 401(k) balance from your salary, contribution rate, employer match and expected return — and see how much of the total comes from the match and from growth.

How this calculator works

A 401(k) grows from three sources: your own contributions, your employer's match and investment returns. The match is the highest-risk-free return most people ever get access to — a 50% match on the first 6% of salary is an instant 50% gain on that money, before any market return. Not contributing at least to the match is leaving compensation on the table.

The projection assumes contributions are made monthly and the salary stays constant. Real salaries rise, so the actual balance is usually higher; the model also ignores plan fees, vesting schedules (employer money you lose if you leave early) and annual contribution limits. It is pre-tax money in a traditional 401(k), so withdrawals in retirement are taxed as income.

The formula

Monthly employee contribution = salary × contribution% ÷ 12. Monthly employer contribution = min(contribution%, match cap%) × salary × match% ÷ 12, i.e. the match only applies up to the cap.

where r = return ÷ 12 ÷ 100 and n = years × 12. The employer match total is the monthly employer contribution × n.

Worked example

On a 80,000 salary, contributing 6% with a 50% match up to 6%, the monthly employer contribution matters: over 30 years at 7% the balance reaches $813,148. Of that, $226,000 is contributions and $587,148 is growth, with $72,000 coming directly from the employer match.

Common mistakes

• Stopping at the match. The match is the minimum, not the target. Most planners suggest 15% of gross pay including the match for a comfortable retirement.
• Ignoring the expense ratio. A 1% fund fee versus 0.05% index funds can cost a third of the final balance over 30 years.
• Cashing out when changing jobs. A cash-out triggers income tax plus a 10% early-withdrawal penalty in the US and permanently loses the growth. Roll it over instead.