401(k) Contribution Calculator

How it works

Each paycheck you defer your contribution percentage of that paycheck's pay. Over a full year that is your salary times the percentage, unless it would pass the IRS elective deferral limit, at which point most payroll systems stop the deferrals for the rest of the year.

Your limit is the elective deferral limit for the tax year plus any catch-up for your age at the end of that year: the standard catch-up from age 50, or the larger catch-up for ages 60 through 63. The limit is the same whether you choose pre-tax or Roth 401(k) deferrals; it covers both combined.

The paycheck in which you reach the limit is the first one where your running total would meet it. A percentage above the one needed to reach the limit only gets you there sooner.

Employer contributions do not count toward your deferral limit, but your deferrals plus everything your employer puts in must stay under a separate total additions limit (IRC §415(c)), or 100% of your pay if that is lower. Catch-up contributions are left out of that total.

A deferral becomes a catch-up contribution when it goes over any IRS limit, not only the deferral limit: if your regular deferrals plus employer contributions would pass the total additions limit, the part of your deferrals over it also counts as catch-up, up to your catch-up amount (Treas. Reg. §1.414(v)-1(b)(1)(i)). Room below zero means some contributions would still be over the limit and the plan would have to correct them.

Formula

limit        = elective deferral limit + catch-up for age (50+, or 60–63)
per paycheck = salary × contribution % ÷ paychecks per year
for the year = min(salary × contribution %, limit)
% needed     = limit ÷ salary
limit paycheck = ⌈limit ÷ per paycheck⌉   (when salary × % ≥ limit)
A = min(total additions limit, salary)    regular = min(for the year, base limit)
over 415(c)  = max(0, regular + employer − A)
catch-up used = min(catch-up, for the year − regular + min(over 415(c), regular))
additions    = for the year + employer − catch-up used
room         = A − additions

Example

In 2026 someone who is 52 at year end, earns $150,000, is paid every two weeks and defers 25% puts $1,442.31 into the plan each paycheck. Their limit is the $24,500 deferral limit plus the $8,000 age-50 catch-up, $32,500 in all, which 21.67% of pay would just reach.

At 25% they reach $32,500 in paycheck 23 of 26, so they contribute $32,500 for the year rather than $37,500. With a 4% employer contribution ($6,000), the additions that count toward the $72,000 total limit are $32,500 − $8,000 of catch-up + $6,000 = $30,500, leaving $41,500 of room.

Assumptions and limitations

• Limits are from IRS Notice 2025-67 for 2026 and Notice 2024-80 for 2025; choose the tax year above. They apply to 401(k), 403(b), governmental 457(b) and Thrift Savings Plan deferrals, not to SIMPLE plans.
• Salary is assumed to be paid evenly across the year and the percentage applies to every paycheck. Bonuses, raises mid-year and the plan's own definition of pay are not modelled.
• The limit is per person across all your 401(k) and 403(b) plans for the year. If you change jobs, deferrals at the first employer count against the same limit.
• For 2026, catch-up must be Roth if your 2025 FICA wages from this employer exceeded $150,000. The threshold is indexed each year (IRC §414(v)(7), added by SECURE 2.0 §603; IRS Notice 2025-67; final regulations, September 2025). The result above shows the rule for the year you choose. This is a note only; the calculator does not split pre-tax and Roth.
• Reaching the limit early can cost employer match if your plan matches each paycheck and has no year-end true-up. Ask your plan administrator.
• The compensation limit on pay that counts for plan purposes (IRC §401(a)(17)) and plan-specific caps lower than the IRS limit are not modelled.
• This is an estimate for planning. It is informational and educational and is not financial, tax or legal advice.

Frequently asked questions