Where each gross dollar actually goes.

Pre-tax first, taxes second, post-tax last.

Payroll runs the same sequence every paycheck: pre-tax deductions come off the top, taxes are computed on what's left, and post-tax deductions (like Roth 401(k)) come out after taxes. Knowing the order is the difference between being surprised by your check and being able to predict it.

• Pre-tax deductions. Traditional 401(k), HSA, and "section 125" cafeteria-plan deductions (most health/dental/vision/FSA) come out of gross before federal tax is computed. HSA + section-125 also reduce FICA wages; Traditional 401(k) does not.
• Federal income tax. Computed on (gross − pre-tax deductions − standard deduction) using the progressive bracket table for your filing status. The calculator uses 2026 brackets.
• FICA. Social Security is 6.2% on wages up to $184,500 (2026 wage base). Medicare is 1.45% on all wages, plus an extra 0.9% above $200k single/HoH, $250k MFJ (combined wages), or $125k MFS.
• State tax. Modeled here as a flat percentage of the same base used for federal taxable income. Real states have brackets, deductions, and credits — the flat rate is good for planning, not for filing.
• Roth 401(k). Comes out after federal/state tax — the contribution doesn't reduce your tax bill this year. The trade-off is tax-free growth and tax-free qualified withdrawals later.

Two tax rates — both true.

Your marginal tax rate is the federal bracket your last dollar lands in — usually 12%, 22%, 24%, or 32% for working households. Your effective rate is the average — total federal tax divided by total income. Effective is always lower than marginal because the lower brackets fill up first.

• Marginal matters for "should I do Roth or Traditional?" Pre-tax contributions reduce income at your marginal rate today. If marginal is high, the deduction is worth more, and Traditional usually wins. If marginal is low (10–12%), Roth often wins.
• Effective matters for budgeting. Your overall federal bill, expressed as a percent of gross. Knowing effective is how you reconcile a paystub with your annual income.
• The calculator shows both. Watch how marginal jumps when you cross a bracket boundary — and how effective barely moves, because only the dollars above the boundary get taxed at the higher rate.

This calculator powers the rest.

The take-home number from here is the input to your budget. The "% of gross" sliders here set the contribution rates that show up in employer match, compound growth, and Roth vs. Traditional. The marginal rate it shows is the input to the Roth vs. Traditional decision.

• Step 2 of the order of operations says to capture the full 401(k) match (after Step 1, the deductible buffer). Try setting your Traditional 401(k) % to your match cap and see how the take-home moves — usually less than you'd expect, because the federal tax savings cushion the contribution.
• Step 6 says "15% of gross to retirement." Bump Traditional + Roth combined to 15% and watch the federal tax line drop. That's the math behind why anchoring on gross matters.

What stays, and what leaves.

"Pay yourself first" sounds like an investing aphorism, but it's really about sequencing. Your gross is the only number you fully own. Below it, every dollar is going somewhere — to the government, the insurance carrier, your future self, your community, the landlord, the grocery store. The question is whether you decide the order or let the order decide itself.

Anchor your retirement, savings, and giving on a percent of gross, and let payroll handle the deductions before the money ever hits your bank. Once those are set, the "Available to spend" line is honest about what's left for everyone else.

• Set the rate, not the dollar. Anchor 401(k), HSA, and giving as a % of gross. They scale automatically when you get a raise, so the priorities don't have to be re-decided each year.
• Automate so they don't compete. Trad and Roth 401(k) come off the top because payroll deducts them before payday. Treat Roth IRA, 529, and giving the same way — schedule them to leave the bank on payday, not the 30th.
• What's left is for everyone else. The "Available to spend" line is what funds rent, groceries, utilities, hobbies — flowing out to landlords, businesses, neighbors. There's no shame in that line; the point of paying yourself first is that this dollar already did its work upstream.

What this doesn't model.

• City and local taxes. NYC, Philadelphia, San Francisco and others add their own income tax — not modeled. Add the local rate to your state-rate input as a rough proxy.
• Tax credits. Child tax credit, earned income credit, dependent care, retirement savings credit — all reduce your federal liability and aren't modeled here. If you take significant credits, your effective federal rate is lower than shown.
• State complexity. Most states have their own brackets and deductions. The flat-rate input is a planning estimate, not a filing-grade calculation. CA, NY, NJ, MN, OR, MA in particular have their own progressive systems.
• Bonus/commission withholding. Bonuses are typically withheld at a flat 22% federal rate (37% above $1M). The actual tax owed is determined at year-end on your full income — withholding ≠ tax.
• Employer-paid benefits. The employer half of FICA, employer health-plan contributions, and the dollar value of the 401(k) match aren't shown. They're real compensation, just not on your paystub.
• Garnishments and post-tax items. Wage garnishments, post-tax insurance premiums, charitable payroll deductions, ESPP — not modeled. Subtract them manually from take-home if relevant.