Scope & Coverage

• Geography: United States (Federal) + all 50 states + DC. Local city/school-district taxes included where verified.
• Frequencies: Weekly (52), Biweekly (26), Semi-Monthly (24), Monthly (12), Annual (1).
• Audience: Primarily W-2 employees; contractors can still use for rough net-pay comparisons.
• Where to start: Browse all State calculators or jump to City calculators.

Inputs We Use

• Location: State and (optionally) city/locality.
• Pay frequency: Weekly / Biweekly / Semi-Monthly / Monthly / Annual.
• Gross pay per period: Base wages for the selected frequency.
• Filing status: Single, Married Filing Jointly, or Head of Household.
• Dependents: Used where a simplified dependent/credit estimate is supported.
• Pre-tax deductions: 401(k) %; HSA/FSA/Insurance $ per period.
• Optional adjustments: We may expose additional fields as coverage expands for specific states/cities.

Pay Frequency & Annualization

We annualize per-period inputs, calculate taxes on the annualized amount, then convert results back to the selected frequency.

Calculation Steps (High-Level)

1. Annualize gross pay using the frequency table above.
2. Subtract pre-tax deductions (401(k) up to IRS limit; HSA/FSA/Insurance $ per period where allowed) to get annual taxable wages.
3. Federal taxable income = annual taxable wages − standard deduction (by filing status).
4. Federal income tax is computed with progressive brackets (marginal rates applied by tier).
5. FICA: Social Security applies up to the annual wage base; Medicare applies to all wages plus an additional surtax above federal thresholds.
6. State income tax: none / flat / progressive depending on the state; some states include unique deductions/credits (see state pages).
7. Local taxes: city/school-district where verified; residency and workplace rules may apply.
8. Net pay per period = gross per period − per-period share of (Federal + FICA + State + Local) − post-tax items (if any).

Worked Example (Illustrative)

Suppose you enter $2,000 biweekly, filing status Single, with 5% 401(k) and $50 HSA per period, in a state with a progressive tax and no local tax:

1. Annual gross: $2,000 × 26 = $52,000
2. Pre-tax deductions (annual): 401(k) 5% → $2,600; HSA $50 × 26 = $1,300 → total $3,900
3. Annual taxable wages: $52,000 − $3,900 = $48,100
4. Federal taxable income: $48,100 − (standard deduction for Single) = taxed by federal brackets
5. FICA: Social Security on wages up to wage base; Medicare on all wages (plus additional surtax if above threshold)
6. State income tax: apply the state’s rules to taxable income (flat vs progressive)
7. Per-period net: Convert annual taxes back to biweekly and subtract from $2,000 gross

To see the exact values for your location, use a state calculator or jump straight to your city calculator.

Federal Income Tax (with FICA)

• Standard deduction reduces federal taxable income and is based on filing status.
• Brackets are applied marginally (each portion of income taxed at its bracket rate).
• FICA: Social Security (up to annual wage base) and Medicare (all wages). An additional Medicare surtax applies above federal thresholds for higher earners.
• Credits & special cases: Our base calculators focus on core withholding and generally exclude complex credits (e.g., EITC) unless noted.

State & Local Income Tax

States vary widely. We model the latest verified structure for each state:

• No-tax states: State income tax is $0.
• Flat-rate states: A single rate applied to taxable income.
• Progressive states: Tiered brackets; we apply marginal rates by tier.
• Special rules (e.g., unique deductions/phase-outs, standard deduction differences): Incorporated where feasible and documented on state pages.

Local (city/school-district) taxes are included where verified. Some localities tax based on residency, others on the workplace, and some on both. When rules are too complex or data is unclear, we either present the best available simplified estimate or note the limitation on the page.

Pre-Tax vs Post-Tax Deductions

• 401(k) / Traditional: Entered as % of gross; reduces taxable wages (subject to IRS annual limits).
• HSA/FSA/Insurance: Entered as $ per period; reduces taxable wages where allowed.
• Roth contributions: After-tax; do not reduce taxable wages (treated as post-tax if a field is provided).
• Post-tax deductions (if a calculator exposes them): Subtracted after tax calculations; they don’t affect taxable wages.

Edge Cases & Limitations

• We model core paycheck withholding and do not replace employer payroll systems.
• Complex credits (EITC/CTC nuances), multiple-job phase-outs, reciprocity agreements, and supplemental wage rules are not always reflected unless noted.
• Local rules may change mid-year; we update verified rates as soon as practical.
• Rounding and timing differences (YTD basis, pay-period accumulation, employer-specific W-4 logic) can produce differences from your paystub.

Troubleshooting Differences vs. Your Paystub

Glossary (Quick Definitions)

Gross pay

Your pay before taxes and deductions for the selected period.

Taxable wages

Gross pay minus pre-tax deductions that reduce taxable income.

Withholding

Estimated taxes taken from your paycheck (federal, state, local, FICA).

FICA

Payroll taxes for Social Security (to the wage base) and Medicare (all wages, plus additional surtax above thresholds).

Effective tax rate

Total taxes divided by gross income—useful for comparisons across offers and locations.

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