Montana paycheck calculator

Two people on the same salary in the same state can bank different amounts every two weeks. The gap comes from things a job offer never mentions: how many pay periods the employer runs, what goes into the retirement plan before tax, and whether the state takes a cut at all.

This tool works the tax out from the annual view and then divides back down, which is roughly how a payroll system does it. What it does not do is guess at your W-4. Everything below explains what the number above is made of, and where it stops.

What does this paycheck calculator actually compute?

It computes federal income tax, Social Security, Medicare and, where the data allows, state income tax on the pay you enter, then subtracts them from gross to give a take-home figure per period. It uses 2026 federal figures. It does not read a W-4, does not apply tax credits, and does not model local or city income tax.

The five inputs are Gross pay per period, Pay frequency, Filing status, State and Pre-tax retirement per period. Nothing else is asked, because nothing else is used.

How this calculator works

The engine annualizes first. Gross pay per period is multiplied by the number of periods in the year: 52 weekly, 26 every two weeks, 24 twice a month, 12 monthly, 1 annually. Pre-tax retirement is annualized the same way. Federal taxable income is annual gross minus annual pre-tax retirement minus the 2026 standard deduction for the filing status chosen.

That taxable figure then runs through the 2026 federal bracket table band by band, not at a single rate. The standard deduction is $16,100 for a single filer and $32,200 filing jointly.

FICA is worked out separately and on a different base. Social Security is 6.2% of annual gross up to the $184,500 wage base, and Medicare is 1.45% of annual gross with no ceiling. Both are charged on gross, before the pre-tax retirement deduction, which is the single most common surprise on this page. FICA and income tax use different definitions of pay, and the tool respects that.

State income tax is computed only when it can be computed honestly. A state with no wage income tax returns zero and says so. A flat-rate state takes annual gross minus annual pre-tax retirement, subtracts that state standard deduction if one is published, and applies the flat rate. A state with graduated brackets returns nothing at all.

Finally the annual deductions are summed, subtracted from annual gross less the pre-tax contribution, and divided by the number of periods.

Why does the state income tax line say "not calculated"?

Because the site holds that state top marginal rate but not its bracket table. Applying a top rate to every dollar of income would overstate the bill, sometimes by thousands of dollars. The tool refuses rather than publishes a wrong number, and the headline changes to "Take-home per period, before state tax" so the figure is not mistaken for a full answer.

New York is a worked case. Its top rate is 10.9%, but almost nobody pays 10.9% on their whole income. A tool that multiplied a $65,000 salary by 10.9% would show about $7,085 of state tax where the real figure is far lower. The refusal is deliberate, and it is described in the caveat under the result.

Flat-rate states are different. One rate and one allowance are enough to compute the whole bill exactly, so those states get a number.

How do I use it, step by step?

1. Put the gross figure from one payslip into Gross pay per period. Gross, not net, and one period, not the year.
2. Set Pay frequency to match how often you are actually paid. Every two weeks is 26 periods and is not the same as twice a month, which is 24.
3. Choose Filing status. Only Single and Married filing jointly are offered. Head of household filers should read the result as an upper bound on the federal tax.
4. Choose your State. If the state income tax line comes back as "not calculated", the take-home figure is before state tax and will be too high.
5. Enter Pre-tax retirement per period if you defer into a traditional 401(k). Enter the dollar amount per period, not a percentage.
6. Read the headline as an estimate of tax, then check the per-year column of the breakdown table. The annual figures are the ones worth comparing against a pay stub in December.

What does a real calculation look like?

A single filer in Colorado earning $2,500 every two weeks, contributing $150 a period to a traditional 401(k), sees a take-home of $1,884.44 per period. Here is every line of that arithmetic.

Two details in that table are worth pausing on. FICA is charged on the full $65,000, not on $61,100, because the 401(k) deferral does not reduce Social Security or Medicare wages. And Colorado standard deduction happens to be $16,100, the same figure as the federal single deduction, so the state taxable base lands at $45,000 as well. That is a coincidence of the two numbers, not a rule.

What is left out of the take-home figure?

Common mistakes

Reading the result as your withholding. The tool estimates the tax owed on the pay. Withholding is what the employer sends the IRS based on your W-4, and the two are different on purpose. If your W-4 claims dependents, your actual withholding will be lower than this figure. Use the IRS Tax Withholding Estimator when the question is whether enough is being withheld.

Entering an annual salary in a per-period box. The field is Gross pay per period. Putting $65,000 into it with a biweekly frequency produces an annualized income of $1.69 million and a wildly wrong answer. The breakdown table has a per-year column: if the annual gross does not look like your salary, the input is wrong.

Confusing biweekly with semimonthly. Twice a month is 24 pay periods and every two weeks is 26. Same salary, different per-period gross, and about an 8% difference in the number the tool shows.

Treating a "not calculated" state as a state with no tax. Blank is not zero. If the line reads "not calculated", state tax is still coming out of the real check. Only the states listed on states with no income tax return an actual zero.

Assuming a 401(k) contribution cuts every deduction. It cuts federal and state taxable income. It does not cut Social Security or Medicare, which is why the FICA line in the example above does not move when the deferral is entered.

When is this the wrong tool?

If your pay varies week to week, an annualized model will mislead you. The engine assumes the period you type repeats all year, so a single big commission month projected across 26 periods overstates the annual income and pushes you into brackets you never reach.

It is also the wrong tool for anyone whose income runs past the Social Security wage base part way through the year. The engine charges 6.2% on annual gross up to $184,500 as a single annual calculation, so it will not show you the mid-year period where Social Security stops and your net pay jumps.

And it is the wrong tool for the self-employed. There is no employer half to skip: the whole 15.3% falls on you, and the self-employment tax calculator is the one that models it.

Before you trust the number

• Check that the per-year gross in the breakdown table matches your actual salary
• Confirm the pay frequency matches your payslip, counting 26 periods for every two weeks
• Enter pre-tax retirement in dollars per period, not as a percentage of salary
• Note whether the state line says "not calculated" and treat the take-home as pre-state if it does
• Add your own health premium and post-tax deductions by hand before comparing to a bank deposit
• Compare the annual federal tax line against last year Form 1040 if your income has not changed much
• Run the IRS withholding estimator if the gap between this estimate and your payslip is large

The federal figures here move every January with inflation adjustments, and the standard deduction and wage base move with them. State rates change more often and with less notice, particularly in states cutting a flat rate year by year. If you are checking a payslip in the second half of the year, check that the tool is running on the same tax year your employer is.