The 401(k) limit runs on the calendar year, and the only money that counts toward 2026 is what comes out of a paycheck dated by December 31. Unlike an IRA, there is no April catch up for a 401(k). Once the last check of the year is paid, the 2026 room is gone.
The calculator above takes what you have put in so far, how many paychecks are left and your age, and tells you how much to contribute from each remaining check to reach the limit. It also flags when part of a catch-up contribution has to go in as Roth.
The 2026 limits
The IRS set the 2026 numbers in November 2025:
- $24,500 is the employee limit for 401(k), 403(b), most 457 plans and the federal Thrift Savings Plan. It was $23,500 in 2025.
- $8,000 is the extra catch-up for people 50 and older, up from $7,500.
- $11,250 is the larger catch-up for people who turn 60, 61, 62 or 63 during the year. It replaces the $8,000 amount for those ages; it is not added on top.
So the most an employee can defer in 2026 is $24,500 under 50, $32,500 from 50 through 59 or at 64 and older, and $35,750 from 60 through 63.
Age is measured at the end of the year. If you turn 50 on December 30, you can make the full catch-up for 2026. The same goes for turning 60.
These limits are per person, not per plan. If you changed jobs this year, add what you deferred at the old job to what you have deferred at the new one. Each employer’s payroll system only tracks its own plan, so neither will stop you from going over.
Employer matching and profit sharing contributions do not count toward the $24,500. They fall under a separate, larger limit of $72,000 for total contributions in 2026, not counting catch-ups.
How to use the result
Most plans let you set your contribution as a percentage of pay, and some allow a flat dollar amount. The calculator gives both: the dollar amount per check and what that is as a share of gross pay.
A few points that come up when people try to max out late in the year:
Changes take time. Many payroll systems need one or two pay periods to apply a new election. If you have four checks left and the change starts on the third, you really have two. Enter the number of checks the new rate will apply to.
Plans cap the percentage. Plans commonly limit deferrals to somewhere between 50% and 90% of pay. If the calculator shows more than that, you will not reach the limit this year, but you can still raise your rate to the plan maximum.
Taxes and premiums come first. Social Security and Medicare tax, health insurance premiums and other deductions still come out of each check. A 60% deferral can leave very little take home pay, so look at what you need for December bills before you change anything.
Watch for match timing. Some employers match each paycheck and do not make up the difference later. If you front load or back load contributions, you can lose part of the match. Others do a year end true up. Your plan’s summary plan description says which applies to you.
The Roth catch-up rule for higher earners
Starting in 2026, if your Social Security wages from your employer were over $150,000 in 2025, any catch-up contribution you make to that employer’s plan has to be Roth. The base $24,500 can still be pretax.
Roth money goes in after tax, so it does not lower your 2026 tax bill. It grows tax free and comes out tax free in retirement if you meet the rules. The calculator splits the remaining room so you can see how much of it is pretax and how much has to be Roth.
If your plan does not offer a Roth option, it cannot accept catch-up contributions from employees above the wage line. Our article on 401(k) catch-up contributions for 2026 goes through this rule in detail.
What it saves on taxes
Pretax contributions come off your taxable wages for federal income tax. In the 22% bracket, each extra $1,000 you defer lowers your 2026 federal tax by about $220. The calculator multiplies your pretax room by the bracket you choose to give a rough figure.
That estimate leaves out a few things:
- Most states also exclude 401(k) deferrals from taxable income, which adds to the saving. Pennsylvania is a well known exception.
- Social Security and Medicare tax still apply to 401(k) deferrals.
- A lower adjusted gross income can help with other items, such as the Saver’s Credit for moderate earners or staying under an income line for a deduction.
If you went over the limit
The calculator warns you if you have already contributed more than your limit. This happens most often after a job change.
Tell one of the plans about the excess deferral and ask it to return the extra amount plus any earnings by April 15, 2027. The returned excess is taxable for 2026. If it is not corrected by that date, the excess is taxed in 2026 and again when you eventually withdraw it.
Other year end moves to pair with this
If you are already at the 401(k) limit, an IRA is the next place to look. The 2026 IRA limit is $7,500, or $8,600 at 50 and older, and you have until April 15, 2027 to contribute for 2026. Our article on funding a Roth IRA and a 401(k) in the same year explains the income limits.
For a fuller list of what has to happen before December 31, see our year end tax deadlines. If a large year end bonus is coming, the bonus tax calculator shows how much will be withheld, and a bigger deferral from that check is one way to hit the limit.
This calculator uses 2026 IRS limits and gives an estimate only. Your plan’s rules and your payroll schedule decide what you can contribute.