Your 401(k) Match: Four Questions to Settle Before You Choose a Percentage

Most 401(k) enrollment screens ask for a single number: the percentage of pay you want to contribute. People often pick something round, like 5% or 10%, without checking what their employer does with that choice. A short list of questions, answered once, can be worth tens of thousands of dollars over a career. The numbers below use an example salary of 70,000 and an example match formula, so replace them with your own.

Question 1: What is the match formula, exactly?

Formulas vary. A common pattern is "50% of what you contribute, up to 6% of your pay". Read it carefully: it does not mean the employer gives you 6%. It means that for the first 6% you put in, they add half as much. On 70,000, 6% is 4,200, and 50% of that is 2,100 from the employer.

Here is how your total changes with your own percentage under that formula:

• Contribute 0%: you put in 0, employer adds 0
• Contribute 2%: you put in 1,400, employer adds 700, total 2,100
• Contribute 3%: you put in 2,100, employer adds 1,050, total 3,150
• Contribute 4%: you put in 2,800, employer adds 1,400, total 4,200
• Contribute 6%: you put in 4,200, employer adds 2,100, total 6,300
• Contribute 8%: you put in 5,600, employer still adds 2,100, total 7,700

Contributing above 6% earns no extra match, but it can still be worthwhile for other reasons. The point is that the match gives each of your first 6 percent a guaranteed 50% instant return, a rate nearly no other investment can promise. Missing it is the cheapest mistake to fix.

Question 2: What does it cost my paycheck?

Less than it looks like, if the contribution is pre-tax (a traditional 401(k)). Pre-tax contributions reduce the income your income tax is calculated on. Suppose, for illustration only, that your marginal federal rate is 22%. Contributing 4,200 reduces your annual take-home by about 4,200 x (1 - 0.22) = 3,276 instead of 4,200, before considering state tax. Spread over 26 biweekly paychecks, a 6% contribution on a gross of 2,692.31 is 161.54 per check, and your take-home falls by about 126.

Two cautions on this estimate. Payroll taxes such as Social Security and Medicare are normally still charged on the full amount, so they do not shrink. And a Roth 401(k) works differently: contributions are made from after-tax pay, so take-home falls by the full amount, in exchange for tax-free qualified withdrawals later. The take-home pay calculator shows how a contribution changes a paycheck for your own figures, which is worth checking before committing to a percentage you cannot afford.

Question 3: What is the cost of leaving some of the match behind?

Say you have decided to contribute 3% because it feels safe. You earn a match of 1,050 a year. Had you contributed 6%, you would collect 2,100. The shortfall is 1,050 a year. Invested at an assumed 7% a year for 30 years (an example rate, not a promise), contributions of 1,050 a year would grow to about 106,100. That is what the missing match costs over a career, and it does not count the 2,100 of your own money that would have grown alongside it.

For the full picture, compare two paths over 30 years at that same assumed 7%:

• Contribute 6% (4,200 a year) plus the full match of 2,100: about 636,800
• Contribute 6% but with no match available: about 424,500

Contributions are assumed flat at each year's start, with no raises. Real life has raises, which push these numbers higher, and market returns, which will not be a steady 7%. The 401(k) calculator lets you add salary growth and change the return assumption to see the effect on your own balance.

Question 4: When does the match become mine?

Your own contributions are always yours. The employer's match may be subject to vesting, a schedule that determines how much of it you keep if you leave. Two common forms are a cliff, where you keep none until a set number of years and then everything, and a graded schedule, where you earn a slice each year.

Suppose the schedule is a 3-year cliff. If you leave after 2 years, you forfeit the match from both years: 2 x 2,100 = 4,200 in this example. If you leave at 3 years, you keep all of it. When you are thinking about a job change, a few months can make the difference between keeping and losing several thousand dollars, so check your plan's vesting date before giving notice. Your plan documents or HR should have the schedule in writing.

A practical order of operations

• Contribute at least enough to capture the full match. This is usually the highest-priority savings step after a basic cash cushion.
• If you carry high-interest debt, such as a card at 22%, weigh paying it down against going beyond the match. Capturing the match first is still common advice because the return is so high.
• Decide between traditional and Roth based on whether you expect a higher or lower tax rate in retirement. If unsure, splitting is a reasonable hedge. See the Roth IRA calculator for how the after-tax math differs.
• Turn on auto-escalation if your plan offers it. Raising your rate by 1% each year is barely felt.
• Revisit when your salary changes. A match is a percentage of pay, so a raise lifts it automatically only if your contribution percentage stays the same.

One more point. Contribution limits, match formulas and tax rules change over time, and plans differ. Treat the numbers here as illustrations of the method and check current limits with the IRS or your plan administrator. To see where steady contributions could take you over a full career, a retirement calculator pairs well with the figures from your own plan.