What do I type into my benefits forms?
New job? Drop in your offer letter and benefits guide. We read the match formula, the HSA and the premium, then give you the exact numbers for each box — before your enrolment window closes.
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How these numbers are worked out
Five rules, all published, and one of them is the reason this page exists rather than a blog post.
Your first week at a job asks you to fill in forms that lock for a year, using numbers that live in a benefits guide nobody reads. This tool reads it for you: the 401(k) percentage that captures your full match, whether Roth or traditional is stronger at your bracket, what to put in the HSA box per paycheck, and what your first full check should be. It is built for the thirty days after a start date, and it is worth nothing outside them — which is why everything it returns is shaped like the form rather than like a plan.
The 401(k) number is your match cap, and nothing above it
The percentage this tool tells you to type is exactly the point where your employer stops matching. That is the one number in your first week with an unambiguous answer: below it you are declining money that is offered to you, and the match is not paid retroactively for months you skipped. What to contribute ABOVE the match is a genuinely different question that depends on high-interest debt, whether you have a cash buffer, and what else is on your plate — and inventing an answer to it from four form fields would be worse than not answering it. That is what the money plan is for.
Roth or traditional is decided by the bracket you land in after contributing
We take your salary, subtract the 2026 standard deduction and your pre-tax contributions, and read the marginal bracket that remains — the rate your next dollar is taxed at, not your average rate. Below 22%, Roth is usually stronger, because you are likely paying the lowest rate you will ever pay and qualified withdrawals later are untaxed. At 22% and above, the deduction today usually wins. The order matters: your own contributions can push you across that line, so reading the bracket before them would give the opposite answer for anybody sitting just above it.
An HSA dollar costs less than a 401(k) dollar, and this is why
A 401(k) contribution escapes income tax but not FICA — Social Security and Medicare still come out of it. An HSA contribution made through payroll escapes both. That is a difference of 7.65 cents on every dollar, permanently, in the HSA’s favour, and it holds regardless of your bracket. Most explanations treat the two as equivalent pre-tax buckets, which understates the HSA every time. The figures on this page price each one separately for exactly that reason.
Everything is converted to your actual pay period
A payroll portal asks for a percentage or a dollar figure per paycheck, not a yearly plan, so that is what this returns. The conversion is not cosmetic: twice a month is 24 periods and every two weeks is 26, they are different numbers, and dividing an annual HSA target by the wrong one leaves you short or over the limit by the end of the year. The tool asks which you are on because there is no way to guess it.
The enrolment date is a prompt to check, not an answer
Thirty days from your start date is the common default, so that is what we show. It is not a rule — plans set their own windows and some are two weeks. The date on this page exists to make you go and find the real one in your benefits email, and it is labelled as a guess everywhere it appears, because being confidently wrong about this costs somebody a year of coverage.
Where this stops These are estimates for planning, not personalised financial, tax or legal advice, and WeLeap is not a registered investment adviser. The federal figures are 2026 single-filer brackets and the standard deduction; if you are married, have dependants, a second job or a working spouse, the W-4 answer here is the wrong one and the IRS withholding estimator is the right tool. State tax is an approximate flat rate rather than a bracket calculation, so treat the take-home figure as close rather than exact. Your employer’s portal is always the authority on what it will accept, and your benefits email is the authority on your real deadline.
Questions people actually ask
How much should I contribute to my 401(k) at my first job?
At least enough to capture the full employer match, and that number is set by your employer rather than by any rule of thumb. A match is money your employer adds only in the months you contribute, and it is not paid retroactively for the months you skipped, so the cost of waiting is permanent rather than delayed. Above the match, how much to contribute depends on high-interest debt, whether you have a cash buffer, and whether an HSA is available — a wider question than this tool answers.
Roth or traditional 401(k) when I am starting out?
It turns on the tax bracket you land in after your contributions come out. Below the 22% bracket, Roth is usually stronger: you are probably paying the lowest rate you will ever pay, so paying it now and taking qualified withdrawals tax-free later is the better trade. At 22% and above, the deduction today usually wins. Your contributions themselves can move you across that line, which is why this tool reads the bracket after them rather than before.
How long do I have to enrol in benefits at a new job?
Usually about 30 days from your start date, but plans set their own windows and some are as short as two weeks. Miss it and the next guaranteed chance is open enrolment in the autumn, which can be most of a year away. The one exception is often the 401(k): many plans let you change your contribution at any time even when health elections are locked, so it is worth asking HR specifically about that rather than assuming everything is closed.
Should I pick the high-deductible plan to get the HSA?
An HSA is the only account that is untaxed going in, untaxed as it grows, and untaxed coming out for medical costs — and a payroll contribution also escapes FICA, which a 401(k) contribution does not. That makes a dollar into an HSA cheaper than a dollar into a 401(k). It is the right call if you are healthy and could cover the deductible from savings. If you have ongoing prescriptions or expect a procedure, the lower-deductible plan is often cheaper overall despite the worse tax treatment.
Why do I need my benefits guide and not just my offer letter?
The offer letter almost never contains the numbers that matter here. Across the real offer letters we tested, every one stated the salary and the work state, and none stated the 401(k) match formula, the HSA contribution or the health premium. Those live in the benefits guide, typically around page 30. That is the document this tool reads for you.
How much will my take-home pay actually drop if I contribute?
By less than you contribute, because a traditional 401(k) contribution comes out before income tax is calculated. A dollar into the plan reduces take-home by less than a dollar — how much less depends on your marginal rate. This calculator shows both figures side by side for exactly that reason: what goes into the account per paycheck, and what it costs you out of take-home once the tax saving is counted. The gap between those two numbers is the part people most often do not expect, and it is usually the reason a contribution that looked unaffordable turns out not to be.
What is the difference between an HSA and an FSA?
An HSA is attached to a qualifying high-deductible health plan, the money is yours permanently, it rolls over every year, it moves with you when you change jobs, and it can be invested. An FSA is offered regardless of plan type, is owned by the employer arrangement rather than by you, is generally forfeited if unspent by the end of the plan year beyond a small carryover, and does not follow you to a new job. Both reduce taxable income. This calculator covers the HSA case, because that is the one tied to a plan choice you are making during enrolment.
Estimates to help you think, not financial advice. See all 10 free calculators.
Once the forms are in
This page covers the first week. These cover the rest.
- Money PlanThis page tells you the one number your first week demands: enough to capture the match. What to do with everything above it — buffer, debt, retirement, and in what order — is the question this one answers.
- Offer Letter AnalyzerStill deciding between offers, or want to know what the package is actually worth before you sign? This prices the whole thing — base, bonus, match, equity, HSA and PTO — as one annual figure.
- Rent AffordabilityThe other decision a new job forces, usually in the same fortnight. This works a rent line off take-home rather than gross, which is the number your landlord’s calculator ignores.
All of them are free and need no account. Browse every WeLeap money calculator.