What will my 401k be worth at retirement?

Three streams fill a 401k, and only one of them is your salary. On the inputs above, 6% of $100,000 is $6,000 a year of your own money. The employer match adds $4,000 on top of that, so $10,000 goes into the account in year one while only $6,000 leaves your paycheck. Over 30 years those two come to $300,000.

Growth is the third stream and eventually the largest one. Starting from $0 today, the same contributions compounding at 7% a year end at $1,016,643, of which $716,643 was never paid in by anyone. That is more than the $300,000 you and your employer put in combined. The reason is time rather than cleverness: the first year's $10,000 has 30 years to compound, and the last year's has one.

The calculator keeps those three apart in the composition bar instead of showing one total, because they are not the same kind of money. Your contributions are a decision you make. The match is a decision your employer already made and is waiting for you to accept. The growth is an assumption you chose, and it is the least reliable number on the page.

A dollar-for-dollar match is an immediate 100% return on the money, before it grows at all, and it is the only return here that does not depend on what markets do. It is also the easiest thing to miss, because nothing tells you it is happening: payroll simply contributes less on your behalf and no line item ever says what you gave up.

Priced out, at $100,000 with a match up to 4%, contributing 2% instead leaves $2,000 of employer money unclaimed every year. Over 30 years that forgone match alone would have been worth $203,329. The whole balance falls from $1,016,643 to $406,657, and roughly a third of that gap is money your employer offered and you declined.

When your contribution rate is under the match threshold the calculator says so in a warning under the answer, with the annual amount and what it compounds to. It is the one piece of advice on this page that is not really a judgement call.

This is the comparison most people are actually running: not whether to contribute, but how much. Salary, match, age, retirement age, and return are held fixed; only the percent changes. The tax column is a full 2025 return computed twice at each rate, not the deferral times a bracket.

Read the employer column first. It rises from $3,000 to $4,000 and then stops, because the match is capped at 4% of pay no matter how much more you defer. Everything above that rate is your own money doing your own work. The step from 3% to 6% adds $406,657 at retirement and is partly funded by your employer; the identical-looking step from 10% to 15% adds $508,321 and is funded entirely by you.

Almost every 401k calculator prices the tax saving as the deferral times your bracket. That is a shortcut, and it fails in both directions.

It is too high when the deferral crosses a bracket boundary. Take $70,000 of salary and a 15% contribution, which is $10,500. The next $100 of that salary is taxed at 22%, so the shortcut claims $2,310 of saving. Running the return twice gives $6,855 of tax without the deferral and $5,015 with it, a real saving of $1,840. The shortcut is $470 too generous, because only the top part of the deferral came off at 22% and the rest fell into the cheaper slice below. Each deferred dollar was worth 17.5%, not 22%.

It is far too low at modest income, and this is the case worth knowing about. At $25,000 of salary, a 6% contribution of $1,500 cuts federal income tax from $928 to $28. That is $900 of saving on $1,500 contributed, a rate of 60.0%, against the $450 a bracket table would have promised: $450 more than the shortcut, and the contribution costs your take-home only $600. The extra is the saver's credit under § 25B, worth $750 here, claimed on Form 8880. It is a credit rather than a deduction, so it comes off the tax itself.

One subtlety the engine gets right and a table cannot: the saver's credit tier is set by your income after the deferral, so contributing more can move you into a better tier and the first dollars deferred are worth more than the last. At $25,000 the first $100 deferred saves 30%, well above the bracket that income sits in.

Five statutory limits shape what can go in, and every one of them is a 2025 figure from IRS Notice 2024-80 rather than a number remembered from a blog post. You may defer $23,500 under § 402(g)(1). From the year you turn 50 you may add $7,500 of catch-up under § 414(v)(2)(B)(i), and at ages 60 through 63 that catch-up is $11,250 instead under § 414(v)(2)(E)(i). A plan may count only the first $350,000 of pay under § 401(a)(17). And everything landing in the account in one year from both sides is capped at $70,000 under § 415(c)(1)(A), with catch-up contributions sitting outside that ceiling.

The calculator applies them in that order rather than showing a percentage the law would not allow. At 61, on $300,000 of salary and a 20% election, the deferral is $34,750 rather than the $60,000 the percentage asks for: the ordinary $23,500 plus $11,250 of catch-up, which is the larger age 60 to 63 amount. At $400,000 the pay cap bites instead: 6% is figured on $350,000 rather than the full salary, so the deferral is $21,000 and the match is computed on the capped number too.

These limits are checked, not asserted. A test in this repository reads the tax engine's own parameter index, which carries the source notice and effective dates for every value, and fails if any constant on this page has drifted from it. When the IRS issues the next year's notice, the test is what tells us before a reader does.

The return. 7% a year is an assumption you typed, not a forecast, and it moves the answer more than any other input: one point either way changes the balance by roughly $225,324. Real markets do not deliver a constant rate, and the order returns arrive in matters as much as their average. Nothing here models fees either, and a percentage point of fund expenses comes straight out of that assumed return.

Inflation and raises. Every figure is in today's dollars with a flat salary, flat contribution limits, and no cost-of-living increases. That keeps the balance readable as buying power, but a real career has raises that lift both the deferral and the match, and the IRS indexes the limits most years. Treat $1,016,643 as what the plan buys in today's money, not the number that will appear on a statement.

The tax you will owe later, and the Roth alternative. A traditional 401k defers tax, it does not cancel it: withdrawals in retirement are ordinary income, and required minimum distributions eventually force them. A Roth 401k reverses the trade, no deduction now and nothing owed later, which is usually the better side of the trade when your current rate is low. This page prices a traditional plan only.

Everything outside the federal return. State income tax, which most states also let you defer and a few do not. Social Security and Medicare tax, which a deferral does not touch at all. Vesting schedules, which can mean the match is not yours until you have been there a few years. Loans, hardship withdrawals, and after-tax contributions. And on the tax side, this models a household with no dependents: children change the child tax credit and the earned income credit, both of which interact with a deferral, so a family should treat the tax saving here as indicative rather than exact. For a married couple the saver's credit is computed on one contributor, so two spouses each contributing would see more credit than this page shows.

This calculator is built to be used without a browser. Every input is a query parameter on this page, and the same parameters on the JSON twin return the complete answer as a document.

GET /tools/401k.json?salary=120000&contribution=10&match=5&status=married-joint

The response carries inputs after parsing and clamping, result with the balance at retirement split into your contributions, the employer match and the growth, a year-by-year yearly schedule, this year's deferral with the statutory limit and catch-up that applied to it, both federal income tax figures and the saving between them, the § 25B saver's credit inside that saving, what the deferral costs your take-home, any employer match left unclaimed and what it would have compounded to, plus sensitivity across a contribution ladder, a return ladder, and all five filing statuses, and limits with the IRS notice they come from, drivers ranked by effect with a plain sentence each, assumptions that say for every field whether you supplied it and name the source when the default came from one, sources with a URL and an as-of date for each source the tool cites, which is an empty list on the calculators whose every default is an example input rather than a published figure, warnings, a disclaimer, and in tool the canonicalUrl and jsonUrl that carry only your non-default parameters. The canonical URL is the answer's permanent address; use it when you cite the number.

Parameters, all optional, in any order:

• salary ($ per year), default $100,000 per year.
• contribution (%), default 6%.
• match (%), default 4%.
• matchRate (%), default 100%.
• age (years), default 35 years.
• retireAge (years), default 65 years.
• balance ($), default $0.
• rate (%), default 7%.
• status (one of single, married-joint, married-separate, head-of-household, qualifying-surviving-spouse), default single.

Values accept plain numbers and loose human formats such as 100k, $100,000, or 6.5%. Unknown parameters are ignored, values outside a field's range are clamped and reported in warnings, and the endpoint never fails on bad input. Responses are cacheable for a day; the defaults change when their sources publish, and tool.version changes when the method does.

• IRS Notice 2024-80 (2025 amounts relating to retirement plans), as of 2024-11-01. The elective deferral limit, the age 50 and age 60 to 63 catch-up amounts, the annual compensation limit, and the annual additions limit for 2025. These are the same figures the tax engine's parameter index carries, and a test pins every constant in this file against it.
• IRS Rev. Proc. 2024-40 (2025 inflation-adjusted items), as of 2024-10-22. The ordinary income rate tables (§ 2.01) the engine applies when it computes the return twice to measure what the deferral saves.
• Public Law 119-21 § 70102 (2025 standard deduction), as of 2025-07-04. The 2025 standard deduction the engine actually applies, which this statute raised after Rev. Proc. 2024-40 had set it. Both returns start from that figure, so it is what decides whether a deferral saves anything at all at low income.
• 26 U.S.C. (Internal Revenue Code), as of 2026-04-21. The sections these limits come from: § 402(g)(1) elective deferrals, § 414(v) catch-up contributions, § 401(a)(17) compensation, § 415(c) annual additions, and § 25B the saver's credit, whose 10, 20 and 50 percent rates the engine also reads from here.

The contribution, catch-up, compensation and annual addition limits are the 2025 amounts in IRS Notice 2024-80, and the rate tables and standard deduction behind the two returns are the parameter authorities the engine itself reports for every computation. A test pins each limit on this page against the engine's parameter index, so these are the numbers the calculation used rather than citations chosen after the fact.

Carlo is a personal finance agent. It knows your accounts, debts, and goals, so instead of a worked example at the salary you typed it can see what you are actually deferring each paycheck, whether you are on track to collect the whole match by December, and what the contribution is really saving you this year. Text it the question.

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