How accurate is this paycheck calculator?

It uses IRS Publication 15-T (2024) and 2024 FICA limits. Results are high-quality estimates; actual payroll can differ due to employer configurations and YTD constraints.

Does it include state/local taxes?

This tool focuses on US Federal withholding only.

How are 401(k) deductions handled?

Traditional 401(k)/403(b) reduce federal taxable wages but not Social Security/Medicare wages.

What about Section 125 plans?

Section 125 (cafeteria plan) deductions reduce both FIT and FICA wages.

When does Additional Medicare Tax apply?

Employers must withhold an extra 0.9% on wages exceeding $200,000 in a calendar year.

Paycheck Calculator

Authoritative Data Source and Methodology

Primary source: IRS Publication 15-T — Federal Income Tax Withholding Methods (2024); SSA 2024 wage base; IRS Additional Medicare tax rules. Calculations mirror your original definitions. :contentReference[oaicite:9]{index=9}

The Formula Explained

Let pay periods/year be $P$, gross wages $W_g$ per period, with:

\[ C_{\text{401k}} = W_g \cdot r_{\text{401k}}, \quad W_{\text{FIT}} = W_g - C_{\text{401k}} - C_{125}, \quad W_{\text{FICA}} = W_g - C_{125} \]

\[ I_{\text{ann}}=\max\!\big(0,\, W_{\text{FIT}}\cdot P + O - D_{\text{std}} - D_{4b}\big),\quad T_{\text{ann}}=\text{TaxBrackets}(I_{\text{ann}},\text{status}) \]

\[ \text{FIT} = \max\!\left(0,\frac{T_{\text{ann}}-C_{\text{dep}}}{P}\right) + E,\quad \text{SS} = \min(B_{\text{SS}}^{\text{rem}},\, W_{\text{FICA}})\cdot 6.2\% \]

\[ \text{MED} = W_{\text{FICA}}\cdot 1.45\% \;+\; \max\!\left(0, \frac{W_{\text{FICA}}\cdot P - 200{,}000}{P}\right)\cdot 0.9\%,\quad \text{Net}=W_g-C_{\text{401k}}-C_{125}-\text{FIT}-\text{SS}-\text{MED}-\text{PostTax} \]

Formulas match your original methodology and labels. :contentReference[oaicite:10]{index=10}

How It Works: A Step-by-Step Example

Inputs: Biweekly; gross = $3,000; Single; 401(k) = 5%; Section 125 = $50; Step 3 credits = $0; no other income/deductions; no extra withholding.
Pre-tax: 401(k) = $150; Section 125 = $50. FIT base = $2,800; FICA base = $2,950.
Annualize FIT income: $2,800 × 26 = $72,800; minus standard deduction $14,600 ⇒ $58,200.
Apply 2024 Single brackets to $58,200 ⇒ annual tax; divide by 26 ⇒ FIT per period.
FICA: SS = min(SS wage base remaining, $2,950) × 6.2%; Medicare = $2,950 × 1.45% (+0.9% if annual > $200k).
Net: Gross − pre-tax − FIT − SS − Medicare − post-tax. :contentReference[oaicite:11]{index=11}

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Frequently Asked Questions (FAQ)

Is my employer’s payroll going to match these results exactly?

Not always. Employers may have additional deductions, rounding rules, benefits, garnishments, or YTD thresholds that alter withholding. This tool provides high-quality estimates based on IRS methods. :contentReference[oaicite:12]{index=12}

Can I include state and local taxes?

This calculator focuses on US Federal taxes only. For a complete estimate, add state, local, and other withholdings separately. :contentReference[oaicite:13]{index=13}

How do I use the dependents credit?

Enter the annual total from W-4 Step 3 (commonly $2,000 per qualifying child under 17; $500 for others). :contentReference[oaicite:14]{index=14}

Does 401(k) reduce Social Security and Medicare?

No. Traditional 401(k)/403(b) reduces federal taxable wages but not Social Security or Medicare wages. Section 125 reduces both. :contentReference[oaicite:15]{index=15}

When does Additional Medicare Tax start?

Employers withhold an extra 0.9% once an employee’s year-to-date Medicare wages exceed $200,000 (estimated here using annualized wages and optional YTD input). :contentReference[oaicite:16]{index=16}

Full original guide (expanded)

Your original content (source attributions, definitions, example, and FAQs) is preserved and harmonized above to strengthen E-E-A-T and readability. :contentReference[oaicite:17]{index=17}