401(k) Calculator

How this 401(k) calculator projects your balance

A 401(k) grows from three sources: the money you defer from each paycheck, the match your employer adds, and investment returns on everything already in the account. This 401(k) calculator runs those three streams year by year until your retirement age. Each year it takes your contribution percentage of that year's salary, caps it at the IRS employee deferral limit ($24,500 for 2026, plus $8,000 catch-up from the year you turn 50), works out the employer match, and grows the balance at your expected return with contributions added monthly. Salary then rises by your expected raise and the next year starts.

The match is the part people get wrong. "50% up to 6%" means your employer adds 50 cents for every dollar you contribute, but only on the first 6% of your salary. Contribute 6% and the match is 3% of salary; contribute 10% and the match is still 3%. Contribute 3% and you only get 1.5%, leaving half the match on the table.

Worked example

Take a 30-year-old earning $75,000 with $25,000 already saved, contributing 8% with a 50%-up-to-6% match, 7% returns and 3% raises. Year one: she defers $6,000, the employer adds $2,250 (75,000 × 6% × 50%), and the account grows by about $2,000, ending near $35,300. By age 65 the projection reaches roughly $1.94 million: $363,000 from her, $136,000 from the employer, and $1.42 million of growth. Growth dwarfs contributions because the early dollars compound for 35 years.

Drop the contribution to 6% and the balance falls to about $1.64 million. Drop it to 3% and it falls to $951,000, because the smaller deferral also halves the match. Capturing the full match is the single highest-return move available in most plans: it is an immediate 50% or 100% gain before any market return.

The 2026 contribution limits

For 2026 the employee deferral limit is $24,500, and workers aged 50 and over may add a $8,000 catch-up (those aged 60 to 63 may be allowed a larger catch-up under SECURE 2.0; check your plan). Employer contributions do not count toward the employee limit, but the combined total is capped separately (generally $72,000 in 2026). The calculator holds the employee limit at the 2026 figure for every future year and marks the years where it bites with an asterisk. In reality the limit is indexed to inflation, so a high earner will usually be able to contribute more than shown later on.

Common mistakes

• Entering the match as a percent of salary. If your plan says "we match 100% of the first 4%", enter 100 as the match and 4 as the limit, not 4 and 4.
• Using a nominal return and reading the result as today's dollars. 7% with 3% inflation is about 4% real. Enter 4% to see the balance in today's purchasing power.
• Forgetting vesting. Employer money may vest over several years. Leave early and part of the match shown here is not yours.

When the projection is misleading

Markets do not deliver 7% every year; a 20-year stretch can average anywhere from 3% to 10%. The gap between those two paths is several hundred thousand dollars on these inputs, so treat the number as a midpoint, not a promise. The model also ignores plan fees, loans and hardship withdrawals, Roth versus traditional tax treatment, and the $360,000 compensation limit on which matches can be calculated. Use it to compare choices you control (contribution rate, retirement age) rather than to predict the exact balance.