How much should I contribute to my 401(k)?

At an absolute minimum, enough to collect the full employer match — anything less leaves guaranteed money behind. Beyond that it becomes a trade-off against other uses of the same dollars: high-interest debt usually beats it, and a cash buffer usually comes first. Set the deferral slider to your employer’s match limit and watch what the employer column does above and below that point.

Does the employer match count toward the annual limit?

Not toward the employee deferral limit, which is the one this calculator applies. There is a separate, much higher overall cap on everything going into the account from all sources in a year, which very few people reach. For almost everyone, the practical constraint is the employee limit shown in the panel.

What happens if I contribute more than the limit?

Excess deferrals have to be returned to you and are taxed in the year they were made, sometimes twice if the correction is late. Payroll systems normally stop your contributions automatically once you hit the ceiling, which is why a high deferral percentage on a high salary often means you stop contributing — and stop receiving the match — before the year ends.

Should I choose the traditional or the Roth option in my plan?

It comes down to whether your marginal tax rate is higher now or in retirement. Traditional wins if it falls, Roth wins if it rises, and they are mathematically identical if it stays the same. The Roth-vs-traditional calculator runs that comparison properly, holding the cost to you today constant rather than comparing two different amounts of money.

What return should I assume?

Use a real, above-inflation return rather than a nominal one, since the contributions in this projection are in today’s dollars. A broad equity portfolio has historically returned around 6–7% real over long periods, and a balanced one less. Whatever you pick, move it a point either way and see how much the answer changes — that spread is the honest range.

Does this include fees?

No, so subtract your plan’s expense ratio from the return you enter. A 1% annual fee against a 7% return is not a 1% haircut on the ending balance — over thirty years it takes closer to a quarter of it, which the calculator will show you if you run it at 7% and again at 6%.

401(k) Calculator — Match, Limits & Growth

Balance by age

Where the money comes from at five-year intervals, with the final year of the projection shown in full.

Projected 401(k) contributions, growth and balance on a $95,000 salary deferring 10.0% at a 7.0% annual return.
Age	Your contribution	Employer match	Growth	Balance
Age 40	$9,500	$2,850	$9,910	$157,660
Age 45	$9,500	$2,850	$18,871	$294,634
Age 50	$9,500	$2,850	$31,439	$486,747
Age 55	$9,500	$2,850	$49,067	$756,196
Age 60	$9,500	$2,850	$73,790	$1,134,111
Age 65	$9,500	$2,850	$108,466	$1,664,157

Contribution and growth columns are that single year’s amounts, not running totals; the balance column is cumulative. Today’s dollars, no fees, no future indexation of the limit.

Contributing at least up to your employer’s match limit is the highest-return move available to you — the match is a guaranteed return before the market does anything.
The employee deferral limit applies to your own contributions only; the employer match sits on top of it and is not counted against it.
The deferral limit steps up once you turn 50, so a projection that spans that birthday should not use one limit throughout.
A traditional deferral defers tax rather than avoiding it — the withdrawal is taxed as ordinary income later.

How the 401(k) calculator works

A 401(k) has three inflows and one compounding engine. You defer a percentage of your salary; your employer matches some fraction of that, usually only up to a capped percentage of pay; and whatever is in the account earns a return. Set those and the calculator runs the account forward, one year at a time, to the age you plan to stop working.

The employer match is the part most people get wrong, so it is split into two inputs. The match rate is how much your employer adds per dollar you defer — 50% means fifty cents on the dollar. The match limit is the percentage of your salary they will match up to. Deferring more than that limit still increases your own contribution, but it adds nothing further from your employer, and the calculator shows the two amounts separately so you can see exactly where that ceiling bites.

The annual limit is applied as a real constraint, not a footnote. If the percentage you set would exceed the published employee deferral maximum, the calculator caps it and says so. That maximum also steps up once you turn 50, and because the projection re-reads it every year, a run that starts at 45 and ends at 65 picks up the higher figure partway through rather than applying the under-50 limit for the whole two decades.

The math

Each year the account earns a return on its opening balance, and the contributions made during that year earn roughly half a year of return — the mid-year convention. Crediting a full year of growth to money that arrived across twelve paycheques overstates a thirty-year projection by several percent, which is the difference between a projection and a sales pitch.

Employee contribution is salary times your deferral percentage, capped at the statutory maximum for your age that year. Employer contribution is salary times the lesser of your deferral percentage and the match limit, times the match rate. Neither is inflated: the limit is a published figure for the current year only, and there is no official schedule for future years, so contributions stay in today’s dollars. Read the return assumption the same way — as a real, above-inflation return rather than a nominal one — and the projection is internally consistent.

The tax figure shown alongside is this year’s only. A traditional deferral comes out before federal income tax, so it reduces your taxable income dollar for dollar, and the saving is your deferral times your marginal federal rate at your current salary. It is not a discount on the contribution — the tax is deferred, not forgiven, and is paid on the way out.

Worked example

On a $95,000 salary, deferring 10% with a 50% match on the first 6% of pay: you put in $9,500 and your employer adds $2,850, for $12,350 a year going into the account. At a 7% return from age 35 to 65, a $60,000 starting balance grows to roughly $1.7 million — of which about $285,000 is your own contributions, $85,000 is the match, and the rest is growth.

Now raise the deferral to 20%. Your own contribution nearly doubles to $19,000, but the employer match does not move at all: it was already maxed at 6% of pay. That is the shape of the decision. The first 6% is the part with a guaranteed 50% return attached before the market does anything; everything above it is an ordinary tax-deferred investment competing with every other use of the money.

Key terms

Elective deferral: The part of your salary you choose to divert into the plan before it is paid to you. This is what the annual employee limit applies to.
Employer match: What your employer contributes on top, expressed as a rate per dollar you defer and a ceiling as a percentage of your pay. It does not count against your own deferral limit.
Catch-up contribution: An additional amount you are allowed to defer once you reach age 50, on top of the standard limit.
Vesting: How long you must stay with an employer before their contributions are irrevocably yours. Your own deferrals are always fully yours from day one.

401(k) Calculator (US, 2026)