Methodology

This page documents how CalcYet estimates compensation and tax outputs. It is designed to help users evaluate model fit, limitations, and appropriate use before relying on calculator results.

Federal Income Tax Methodology

Federal withholding estimates follow IRS Publication 15-T (2026) withholding tables and the progressive bracket system:

1. Gross wages: Annual income from all sources (salary, wages, supplemental income).
2. Standard deduction: Applied based on filing status (single: $16,100; MFJ: $32,200; HOH: $24,100 for 2026).
3. Taxable income: Gross wages minus standard deduction and any additional deductions claimed on W-4.
4. Progressive brackets: Tax is calculated using 2026 federal bracket rates (12%, 22%, 24%, 32%, 35%, 37%).
5. Credits applied: Eligible credits (child tax credit, child and dependent care credit, etc.) reduce tax liability dollar-for-dollar.
6. Pay-period conversion: Annual tax is converted to per-paycheck withholding by dividing by number of pay periods.

FICA Tax Methodology

FICA taxes consist of two components:

• Social Security (6.2%): Applied to all wages up to the 2026 wage base limit of $168,600. Once the limit is reached in a year, Social Security withholding stops.
• Medicare (1.45%): Applied to all wages with no cap. Additionally, the Additional Medicare Tax (0.9%) applies to wages over $200,000 (single) or $250,000 (married filing jointly).
• Self-employment (15.3%): For 1099 contractors, applies to net self-employment income (15.3% is both employee and employer portions combined). A deduction of 50% of self-employment tax is allowed.

State Tax Methodology

State tax estimates use baseline effective rates based on state income tax status:

• No income tax states: Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, Wyoming, and New Hampshire (interest/dividends only) show 0% state tax.
• Flat-tax states: Applied a fixed rate (Colorado 4.63%, Illinois 4.95%, etc.) to taxable income.
• Progressive states: Simplified effective rates used for planning purposes. Actual state withholding may vary by detailed filer situation.
• Local taxes: Not modeled. Cities and counties in states like OH, PA, NY may have additional income taxes not reflected in these estimates.

Core model structure

• Gross compensation is derived from salary/hourly inputs and schedule assumptions.
• Federal tax estimates use simplified progressive bracket logic with baseline filing assumptions.
• FICA estimates include Social Security and Medicare payroll components.
• State taxes are modeled as baseline state-level effective estimates for planning.

Calculator-specific notes

Take-Home Pay

• Includes federal, FICA, and baseline state tax assumptions.
• Returns annual, monthly, and biweekly net pay estimates.

W-4 Calculator

• Estimates per-paycheck federal withholding from annualized inputs.
• Supports filing status, credits, deductions, and optional extra withholding.

1099 Calculators

• Starts from gross contractor income and deductible expenses.
• Estimates self-employment tax, federal income tax, state tax, and quarterly targets.

Salary/Hourly and Overtime Converters

• Use deterministic gross-pay arithmetic based on hours/week and weeks/year inputs.
• Do not estimate taxes unless explicitly combined with tax tools.

Assumptions

• Scenarios are planning-oriented and may not reflect every payroll edge case.
• Benefits elections, local taxes, and advanced filing situations are often excluded.
• Preset pages use standardized assumptions for consistency and comparability.

Known limitations

CalcYet calculators are planning tools. Be aware of these limitations:

• Pre-tax benefits not modeled: HSAs, 401k contributions, FSAs, and dependent care plans reduce gross wages before tax calculation, which we do not model. Your actual tax may be lower.
• Itemized deductions: Only standard deductions are modeled. If you itemize (mortgage interest, property taxes, charitable donations), actual tax may be lower.
• State and local tax (SALT) cap: Federal law limits SALT deductions to $10,000. This may affect marginal rate calculations in high-tax states.
• Advanced credits: Education credits (AOTC, LLC), adoption credit, senior/dependent care credits, and refundable credits are not modeled.
• Rounding and employer implementation: Payroll systems round differently. Final withholding may differ by $1–5 per check.
• Multi-job scenarios: If you have multiple employers, each withholds independently. This may result in over-withholding or under-withholding when combined on your annual return.
• State-specific rules: Some states have local income taxes, additional credits, or deduction rules not captured in simplified state estimates.
• Not legal or accounting advice: These tools are for planning and education. Always verify with a CPA or tax professional for final decisions.

Update cadence

• High-impact pages are reviewed when material IRS/state guidance changes.
• Tax-year references are updated during annual rollover windows.
• User-reported issues are triaged and patched based on severity.

Primary references

• IRS Tax Withholding Estimator
• IRS Publication 15-T
• IRS Form 1040-ES
• U.S. Department of Labor - Overtime Pay

Last updated: February 22, 2026