How 401(k) matching works

An employer match is extra pay deposited into a workplace plan, on terms the plan document sets. The common quote, a 50 percent match on the first 6 percent, means the plan pays fifty cents for each dollar you defer until your deferral hits 6 percent of pay, and nothing extra after that.

The identity is

$$M = S \times \min(d, c) \times m$$

$S$ is salary, $d$ the deferral rate, $c$ the cap the match applies to, and $m$ the match rate, all as decimals. On $80,000 the cap is $0.06 \times 80000 = 4800$ of your own money. At a 50 percent match rate the plan then pays half of that, $2,400, which is 3 percent of pay.

Defer 6 percent and you capture 100 percent of the match. Defer 3 percent and you capture half. Defer 10 percent and the match is still $2,400: the extra 4 percent is yours alone. That leftover, when you stop short of the cap, is the number this page exists to make visible. It is not a fee and it is not interest. It is pay the plan had already offered and that a lower deferral declined.

The calculator above opens on those figures because they are the first worked example. The employer match explorer is the same identity as a picture: drag the deferral across the cap and watch the match flatten.

In the United States a 401(k) is the usual workplace wrapper this match sits inside. A 403(b) or 457 plan is the same idea under a different tax-code section. An IRA cannot receive an employer match. The 401(k) against IRA comparison is that wrapper split. This page is the match formula.

The match has a ceiling. Your own contribution does not. A 10 percent deferral on $80,000 is $8,000 of your money plus the same $2,400 of match, $10,400 combined. A 6 percent deferral is $4,800 plus $2,400, $7,200 combined. The match is identical and the totals are not, because the extra 4 percent is still going in.

What the cap changes is the return on the next dollar. Inside the cap, each dollar you defer brings fifty cents with it, a 50 percent instant return before any market does anything. Past the cap, the next dollar brings nothing extra from the employer. That is why the usual order in a workplace plan is: defer enough to take the whole match, then look at the rest of the tax deferred picture, not the other way around.

The match cap is a percent of pay. The annual contribution limit is a separate ceiling and, in the United States, counts your deferral rather than the match. Hitting the match cap and hitting the annual limit are two different ceilings and they do not move together. The dollar figures on those statutory limits are rewritten, so they are numbers to look up for the year you are funding rather than to bake into a formula.

Some plans pay 100 percent of the first 3 percent and 50 percent of the next 2 percent. That is two applications of the same formula, not a different idea: run the first tier, run the second, add them. The calculator stays on one rate and one cap so the kink at the cap is visible rather than buried in a second slider.

A match unclaimed this year is not only this year's dollars. If the same gap repeats, it is a missing deposit into a compounding stream. On the $80,000 salary, deferring 3 percent instead of 6 percent leaves $1,200 of match on the table each year. Combined contributions that year are $3,600 rather than $7,200. Paid in monthly and compounded at 7 percent for 30 years, that leftover stream grows to $121,997.10, the same figure the captured half of the match grows to, because the two halves are the same size.

The full match stream, $2,400 a year on the same 30-year 7 percent path, reaches $243,994.20. That is the future value of the employer line alone, not of your deferral. Your own $4,800 a year is a separate stream, and it compounds whether or not the match is taken.

That 7 percent is an illustration, not a forecast. A lower return shrinks the future value and a higher one raises it, and a real return sequence is uneven, so the future-value line is the arithmetic of one constant rate. What does not depend on the rate is the first-year gap: $1,200 unclaimed is $1,200 unclaimed at every return, including zero.

The compound interest calculator is the same growth engine pointed at any stream. This page stops at naming how large the match stream is, and what the unclaimed half grows to if the gap repeats.

Vesting sits outside the arithmetic. Some plans hand the match over as it is paid; some require years of service before it is yours to keep. The formula on this page counts the match as credited. Whether it would survive a job change is a plan-document question, not a formula one. Employee deferrals themselves are yours from the day they go in.

The match, in a United States workplace plan, is typically pre-tax on the way in even when your own deferral is Roth. A traditional deferral cuts taxable income this year; a Roth deferral does not. Those are tax facts, and they belong beside this calculation rather than inside it. The Roth against traditional comparison is the tax-timing choice. This page does not pick it.

Payroll is the practical difference that makes the match get taken. A 401(k) deferral leaves the bank account before the pay does. The match is computed on that deferral. An IRA contribution has to be made on purpose, and it cannot receive this match at all.

The 401(k) is a wrapper around ordinary investments. The match is extra pay that wrapper can receive. The same index fund returns the same amount in a 401(k) or an IRA; what the match changes is how much goes in this year before any return is earned.

After the match is captured, the next unit of currency is a comparison of fees, menu and tax treatment rather than a comparison of free money. A workplace plan with high costs and a short list can lose that comparison to an IRA even while the match itself is still worth taking. The tax-advantaged accounts guide is the place that comparison sits in the wider set of wrappers.

Maxing the 401(k) before opening an IRA is a rule of thumb, not a result, and it skips the fact that the two caps are separate. Workplace deferrals do not fill the IRA cap. Filling the IRA does not fill the workplace cap. The usual sequence in the United States is: enough payroll deferral to take the whole match, then a decision about the IRA, then a decision about deferring past the match up toward the workplace cap.

It is not choosing a deferral for you. Inside the cap, the match is an instant return on the next dollar that no portfolio can copy. Whether that dollar is available, and whether a high-interest balance should be cleared first, is a household question this page does not answer. The arithmetic only names what the unclaimed match is worth.

It is also a single-tier match on one salary. Two jobs, a mid-year raise, or a plan that matches only up to a dollar cap rather than a percent of pay are different inputs. Enter the rate and cap your plan actually prints.

The figures throughout are a teaching salary: $80,000, a 50 percent match on the first 6 percent, deferrals of 6, 3 and 10 percent, and a 7 percent illustration for the 30-year stream. They are there so every published number can be re-derived. They are not a recommendation about how much any household should defer. This is educational material, not financial advice.