Methodology
How PayStubIQ estimates paychecks
PayStubIQ combines gross-pay math, federal withholding, FICA, and user-entered state tax and deductions. Missing state amounts are labeled, not guessed.
What the calculators are designed to answer
The site focuses on practical paycheck planning: how a wage converts across pay periods, how much gross pay may be left after common payroll taxes, and how deductions or extra withholding can change a paycheck. It is not a filing system, payroll processor, or legal tax opinion. The goal is to make the assumptions visible enough that a worker can compare job offers, plan a bonus, estimate a 1099 set-aside, or check whether a paystub is broadly in line with expectations.
Every calculator keeps gross pay, taxes, and deductions separate. That structure is intentional: when an estimate changes, users should be able to tell whether the difference came from wage input, pay frequency, filing status, pre-tax deductions, post-tax deductions, state assumptions, bonus treatment, or local tax entries.
Gross pay and pay frequency
Hourly estimates start with hours worked, overtime inputs, and the selected pay frequency. Salary estimates convert annual pay into a per-paycheck amount using the selected frequency. Supported frequencies include weekly (52 checks per year), biweekly (26 checks per year), semimonthly (24 checks per year), monthly (12 checks per year), annually (1 checks per year). Conversion tools use 40 hours per week and 52 weeks per year as defaults, but the calculators let users change those assumptions when their schedule is different.
Federal and FICA assumptions
The paycheck calculator follows the 2026 IRS Publication 15-T Worksheet 1A annualized withholding method and supports Form W-4 Step 2(c), Step 3, Step 4(a), and Step 4(b) adjustments. Annual income-tax liability tools use the separate 2026 standard deduction and marginal tax brackets because liability and paycheck withholding are not the same calculation. Social Security and Medicare are modeled separately using the 2026 Social Security wage base; employer Additional Medicare withholding begins after $200,000 of wages regardless of filing status. Real payroll can still differ because of benefit setup, employer configuration, special wage treatment, and rounding rules.
State tax treatment
State withholding is not automatically calculated. Use an amount from payroll or an official state worksheet. Until an amount is entered, results for states with wage income tax explicitly exclude that tax. Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, Wyoming do not impose a general wage income tax, but state payroll programs, local taxes, and obligations to another state may still apply. Pre-tax comparison tools show federal effects only. Paystub Checkup carries your reported state tax through the arithmetic without rating its correctness.
Deductions and extra withholding
Pre-tax deductions are modeled before taxable income where applicable, while post-tax deductions are subtracted after estimated tax. Extra withholding is treated as an additional paycheck reduction so workers can see its direct cash-flow effect. This makes 401(k), HSA/FSA, insurance, garnishment, and voluntary withholding scenarios easier to compare without blending all deductions into one opaque number.
How to read an estimate responsibly
Start with a baseline
Run a simple case first: normal gross pay, state, filing status, and pay frequency. This gives you a clean comparison point before adding overtime, bonuses, or deductions.
Add one change at a time
Change deductions, extra withholding, bonus method, or local tax one at a time. The per-paycheck and annual results make it easier to see what each assumption changes.
Compare with a paystub
Use a recent paystub to calibrate real-world items such as benefit deductions, local tax labels, and employer-specific withholding behavior.
Important limitations
Paycheck estimates can differ from actual payroll because employers use payroll software, year-to-date wage history, benefit elections, garnishments, local tax setup, reciprocal-state handling, and rounding rules that are not always visible from a simple calculator input. Some jurisdictions also change rates, thresholds, credits, surcharges, or local payroll rules during a tax year.
The calculators are best used for planning and comparison. Users should verify important tax decisions with payroll, the relevant tax agency, or a qualified professional, especially for multi-state work, nonresident taxation, equity compensation, high bonus income, business deductions, or major withholding changes.
Official sources and update policy
Correction, September 20, 2026: we withdrew the old state approximation tables after finding outdated rates and insufficient filing-status handling. A year label did not make those tables verified. State amounts now come from your inputs. We also separated current-check FICA from full-year projections and tightened paystub arithmetic reconciliation to one cent. These are software corrections, not independent professional certification.
The self-employment tool estimates incremental federal income tax from business profit on top of entered full-year W-2 wages. It excludes QBI, credits, and other household income. Only the regular Social Security and Medicare employer-equivalent share is deductible in that model; Additional Medicare Tax is not. Quarterly figures are reserves divided by four, not verified installment payments. Federal withholding and final income-tax liability remain different calculations.
- IRS Publication 15-T (2026), Federal Income Tax Withholding Methods
- IRS Revenue Procedure 2025-32, 2026 tax brackets and standard deductions
- SSA 2026 contribution and benefit base
- IRS Topic 751, Social Security and Medicare withholding rates
- IRS Publication 15, supplemental wages and payroll taxes
- IRS Topic 554, self-employment tax
- Find the official agency for your state withholding worksheet