Retirement & 401(k) Growth Calculator

How 401(k) growth is calculated

Three inputs drive the result: what you contribute, what your employer adds, and what the balance earns. Each year your contributions and any match go in, then the whole balance compounds. Repeat for as many years as you have until retirement.

The employer match is the part worth understanding properly. A common structure is “50% of contributions up to 6% of salary” — meaning if you put in 6%, your employer adds 3%. That’s an immediate 50% return on the money you contributed, before the market does anything at all. No investment reliably offers that.

A worked example

On a $60,000 salary, contributing 6% with a 50% match up to 6%, earning 7% a year for 30 years:

You contribute $3,600 a year. Your employer adds $1,800. After 30 years the balance reaches roughly $510,088. Without the match, the same contributions would grow to about $340,059.

The match is worth around $170,029 of that ending balance — from $54,000 of employer money over 30 years. The rest is compounding on money you never had to earn.

Getting the order of operations right

For most people the sequence is: contribute enough to capture the full employer match, then build an emergency fund, then clear high-interest debt, then increase retirement contributions further. The match comes first because a guaranteed 50% return beats paying down even a 25% APR card.

Once the match is captured, whether to send additional money to a 401(k) or a Roth IRA depends on your tax situation. Our guide on which retirement account to fund first covers that decision.

Common mistakes people make with 401(k)s

• Contributing below the match threshold. If your employer matches up to 6% and you contribute 3%, you’re declining part of your compensation.
• Not checking the vesting schedule. Matched funds often require staying two to four years before they’re fully yours. Worth knowing before changing jobs.
• Leaving the default fund unexamined. Automatic enrolment sometimes defaults to a conservative or expensive fund. Check the expense ratio — the gap between a 0.05% index fund and a 0.75% active one compounds into real money.
• Cashing out when switching jobs. Early withdrawal typically means income tax plus a 10% penalty, and it resets the compounding clock.

What this calculator doesn’t account for

It applies a constant annual return, which real markets don’t provide. It doesn’t model IRS contribution limits, which change annually and cap what you can add. It excludes fees, taxes on eventual withdrawals, salary increases, and any employer match cap in dollar terms. Confirm your plan’s specific match formula and vesting rules with your HR department — they vary widely between employers.