401(k) Contribution Calculator

Work out the exact per-paycheck amount that lands you on the annual limit in December, and what filling it early costs you in employer match.

Most contribution calculators turn a percentage into a dollar figure. The useful question runs the other way. It's September, payroll has already sent some of your money, and you want the rate that lands you exactly on the §402(g) limit in December without overshooting it.

The limit is yours, and payroll doesn't police it

For 2026 you can defer $24,500 of your own pay under IRC §402(g), rising to $32,500 from age 50 and $35,750 in any year you're 60 to 63. The ceiling follows the person, so it's the same ceiling whoever writes the paycheck.

That matters if you changed jobs. Two employers in one year means two payroll systems, neither of which can see the other, and both will happily take your money past the single §402(g) ceiling. The correction is yours to ask for, and the deadline is 15 April. Every ceiling, with the code section behind it, is set out separately.

Working the per-paycheck figure out by hand takes four numbers

Take your §402(g) limit for the year, subtract what payroll has already sent, divide by the pay periods you have left, and then divide that by your gross pay a period to get the percentage the payroll form actually asks for.

1. Find your limit. At 42 that's $24,500; from 50 it's $32,500, and in any year you're 60 to 63 it's $35,750.
2. Subtract the year-to-date figure off your last payslip. With $9,000 already sent, the room left is $24,500 less that $9,000.
3. Divide by the pay periods still to come. Ten of them puts $1,550 into every remaining cheque.
4. Convert to a percentage, because payroll wants one. $85,000 over 26 cheques is $3,269.23 of gross a period, and $1,550 out of that is 47.4%.

Which is where this stops being arithmetic. A 47.4% election is legal, because the §402(g) limit is the only statutory ceiling on a deferral, but plenty of plans cap the election lower in the plan document and payroll simply won't take the number. It also leaves very little to live on across ten fortnights, which is why most people who run this in September land somewhere short of the ceiling.

Two figures get mixed up at step two. Counting the employer match in your year-to-date total makes the room look smaller than it is, because the match sits outside the §402(g) limit altogether, and counting a Roth deferral as though it were separate does the opposite, since one limit covers pre-tax and Roth together.

Filling the limit early can cost you real money

A contribution calculator that ignores the match is worse than useless.

Most plans work out the match on each pay period in isolation. Defer 6% this fortnight and the employer adds its share of that fortnight. Defer nothing, and it adds nothing. So a rate of 25% that fills $24,500 by mid-October leaves five or six paychecks in which you contribute zero, and in every one of them the match is simply not paid.

On a $90,000 salary with a 50% match on the first 6%, that's roughly $104 of match a fortnight. Six missed periods is about $623 gone, for no reason other than pacing.

Some plans fix this with a true-up: after year end they compare what you should have received across the whole year against what you actually got, and pay the difference. It's a plan design choice and no IRS rule obliges an employer to offer it. Your summary plan description will say. Ask before you front-load. There's no fixing it in January. What your match is worth over a career is the larger version of the same question.

One caveat I can't resolve for you. This page assumes the match is worked out on each pay period, which is how most plans I've seen run it, but plan documents vary more than any calculator can know and some compute the match on the whole year's pay. If yours does, the front-loading warning above simply doesn't apply to you, and I'd rather you checked the document than trusted me.

When front-loading is still the right call

A true-up changes the arithmetic completely. Where your plan pays one, timing costs you nothing, and money invested in January has eleven more months of growth than money invested in December. Over a thirty-year career that's worth having. The other case is a job you expect to leave mid-year, where contributing early is the only way to use a §402(g) allowance you'd otherwise lose when the payroll stops.

Outside those two, even pacing is the safer default.

The rate that reaches the limit is not the rate you should choose

Worth saying plainly, because this page is easy to misread. Maxing out is an arithmetic target, not a recommendation. $24,500 a year is more than most households can spare, and there are good reasons to stop well short of it: a high-interest debt, no emergency fund, or a 401(k) whose fees make money above the match better saved elsewhere.

The honest order is the boring one. Claim the entire match first, because nothing else offers a guaranteed immediate return. Then find out what your plan charges, because a 1% annual fee removes close to a fifth of a working life's balance. Only then does filling the rest of the limit become the obvious move. The rate that reaches your own target is a different calculation from the rate that reaches the statutory one, and for most people it's the more useful number.

Percentage or dollar amount, and why plans prefer percentages

Payroll systems mostly take a 401(k) election as a percentage of pay, and that has a quiet advantage: a pay rise lifts the dollar contribution on its own, without anyone having to decide anything.

It also has a failure mode. Above $360,000 of compensation, IRC §401(a)(17) stops the plan from counting further pay, so a percentage election stops growing there even though your deferral limit hasn't been reached. High earners on a fixed percentage can finish the year short of the limit without noticing. The calculator says when that happens.

What this changes in your paycheck

A pre-tax deferral reduces take-home by less than the amount deferred, because it comes out before federal income tax. It does not reduce Social Security or Medicare, which are charged on full wages either way, so the saving is smaller than your marginal rate alone suggests. The paycheck calculator prices a specific change at your salary and filing status.

If you're choosing Roth instead, the deferral limit is the same and shared. The difference is only when the tax is paid.

And if the plan's fees are poor, an IRA is the usual next home for money above the match. What you may put into one depends on your income. A 401(k) never applies that test.

Frequently asked questions

How much should I contribute per paycheck to max out my 401(k)?

Take your limit for the year, subtract what payroll has already sent, and divide by the number of pay periods left. At $24,500 with 26 pay periods and nothing contributed yet, that's about $942 a period. The calculator above does it from your own figures, including the catch-up if you're 50 or over.

Can I contribute more than the limit if I have two jobs?

No. The $24,500 deferral limit belongs to the person, so it covers every 401(k) you pay into during the year. Neither employer can see the other's payroll, so nobody stops you, and the excess has to be caught by you. Two jobs in one year is the most common way people breach it, and the second employer has no idea the first one exists.

Does the employer match count toward my contribution limit?

Not toward yours. The match is an employer contribution, and it sits entirely outside the $24,500 deferral limit that governs the money you defer yourself. It counts instead toward the combined $72,000 ceiling in IRC §415(c), which almost nobody reaches.

Is it bad to max out my 401(k) early in the year?

Front-loading can cost you, for one reason: the match. Most plans calculate the match on each pay period's deferral, so once you hit the limit in October there's nothing to match in November and December and that money is never paid. Some plans run a true-up. No IRS rule requires one, so check your own plan document before you front-load anything.

What happens if I contribute too much to my 401(k)?

Ask one of the 401(k) plans for a corrective distribution of the excess plus its earnings before 15 April of the following year. Inside that window it's taxed once. Miss it and the same dollars are taxed in the year you deferred them and again when they finally leave the plan.

How do I change my 401(k) contribution amount?

Your contribution rate is a payroll election, not an investment decision, so it changes with your employer or its payroll provider. Most plans allow a change every pay period; some restrict it to a monthly or quarterly window. The change applies to future paychecks only, which is why a December correction rarely fixes a year.