401(k) Calculator

The employer match is compensation, not a bonus

The most valuable line item in a 401(k) plan is usually the employer match. It is compensation the plan sponsor has already agreed to pay, contingent on you deferring enough salary to trigger it. Contributing anything below the cap is the same as declining part of your pay. Most participants who plateau under-contribute for years before realizing the miss compounds silently.

The mechanics in this tool follow the common structure. You defer a percent of salary. The employer matches a fraction of that deferral, up to a cap expressed as a percent of pay. A 50 percent match up to 6 percent is a common shape. If you defer 4 percent, you get a 2 percent match. If you defer 10 percent, the match still stops at 3 percent of pay.

Contribution limits, catch-ups, and the SECURE 2.0 super catch-up

The 2025 elective deferral limit is $23,500. Participants age 50 or older can add a $7,500 catch-up. SECURE 2.0 introduced a super catch-up for ages 60 through 63 of $11,250, which materially expands the deferral window for late-career savers. These numbers change on an IRS schedule, so review them annually against the current IRS notice before setting a percent-of-pay election.

Traditional vs Roth 401(k)

Both live inside the same plan and share the same total limit. The traditional side lowers taxable income today and is taxed at withdrawal. The Roth side is funded with after-tax dollars and grows tax-free, with qualified distributions untaxed. The right split turns on the comparison between your current marginal bracket and the bracket you expect to occupy in retirement, factoring in state tax, Social Security taxation, and Medicare IRMAA thresholds.

Compounding is the quiet variable

The projection compounds monthly. That detail matters more than it appears. A 7 percent annual return, compounded monthly, produces a different curve than the same rate compounded annually, and the gap widens across 30 years. The dominant lever in any retirement projection is not the return assumption. It is time in the market plus the discipline of never lowering the deferral election when budgets get tight.

What the tool does not model

The projection ignores fees, vesting schedules on the employer match, plan loans, hardship withdrawals, and Roth-versus-traditional tax treatment at distribution. It also ignores Required Minimum Distributions, which kick in later at the workplace-plan side once you are separated from service or reach the SECURE 2.0 begin age. Use the number here as an order-of-magnitude anchor and coordinate with a CPA before making elections that materially change cash flow.