Methodology
How PayStubIQ estimates paychecks
PayStubIQ is built for planning, comparison, and paycheck sanity checks. The calculators combine gross-pay math, federal payroll assumptions, FICA, state rules, and user-entered deductions to produce transparent estimates.
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 pages use the state selected by the user and apply the state rule set available in the app. States without wage income tax are treated separately; the current no-income-tax group in the app includes Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, Wyoming. Other state estimates may use flat, progressive, or simplified rule structures depending on the state data available. Local taxes are not silently assumed; users can add a local tax input when they know one applies.
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
Federal assumptions were reviewed on July 13, 2026. We update the model when the IRS or Social Security Administration publishes a new tax-year figure. State results remain simplified planning approximations because state withholding certificates, deductions, credits, local taxes, and employer tables vary.