401(k) Calculator: Match, Growth & Payout by Age

A 401(k) projection is a future value calculation on a growing annuity. The existing balance compounds at (1 plus r divided by 12) raised to the number of months, while each monthly contribution compounds for whatever months remain, producing the annuity factor (compound factor minus one) divided by the monthly rate. The employer match is what distinguishes this from a generic investment projection. A typical formula, 50 percent of contributions up to 6 percent of pay, is a two-stage cap: the match applies only to the portion of the contribution that falls within 6 percent of salary, and then only at 50 cents on the dollar. On a 75,000 dollar salary that caps the match at 2,250 dollars a year no matter how much more the employee defers, which is why contributing below the match threshold forfeits guaranteed money. Statutory limits bound the exercise. For 2026 the elective deferral limit is 24,500 dollars, with an 8,000 dollar catch-up at age 50 and a higher 11,250 dollar catch-up for ages 60 through 63 under SECURE 2.0, and a combined employee-plus-employer limit of 72,000 dollars. Distributions are penalty-free from age 59 and a half, with a 10 percent additional tax before that outside listed exceptions, and required minimum distributions begin at 73. The model's main weakness is that it applies a single constant return, commonly assumed at 6 to 8 percent nominal, whereas real markets deliver sequence risk. It also ignores investment fees, salary growth, inflation, vesting schedules on employer money, and the income tax due on traditional withdrawals.

The 401(k) exists because of a short subsection added almost incidentally to the Revenue Act of 1978, which created Internal Revenue Code section 401(k) permitting employees to defer a portion of salary into a qualified profit-sharing plan without current taxation. The provision drew on the Employee Retirement Income Security Act of 1974, which had built the modern regulatory framework for private pensions after the collapse of Studebaker's plan in 1963 left thousands of workers with little or nothing. Benefits consultant Ted Benna is generally credited with recognizing in 1980 that the language allowed a salary-deferral plan with an employer match, and with designing the first such arrangement; the IRS issued proposed regulations sanctioning the approach in 1981. Adoption was rapid, and the 401(k) steadily displaced the defined-benefit pension as employers shifted longevity and investment risk to workers. Later legislation shaped how the plans behave. The Pension Protection Act of 2006 blessed automatic enrollment and qualified default investment alternatives, drawing on behavioral economics research by Richard Thaler, Shlomo Benartzi, and Brigitte Madrian showing that defaults dominate participation rates, and it accelerated the use of target-date funds. The SECURE Act of 2019 raised the required minimum distribution age to 72, and SECURE 2.0, enacted in December 2022, moved it to 73, expanded catch-up contributions for workers aged 60 to 63, and mandated automatic enrollment for most new plans.