1. What is US Federal Income Tax?

The US federal income tax is a progressive tax system where tax rates increase as taxable income increases. It's calculated using marginal tax brackets that vary based on filing status.

2. How Does the Calculator Work?

The calculator uses the US federal tax formula:

Where:

• Taxable Income — Your annual income after deductions
• Progressive Tax Rate — Varies by income bracket and filing status
• FICA — Social Security (6.2%) and Medicare (1.45%) taxes

3. Understanding Progressive Tax Rates

Details: The US uses marginal tax brackets where different portions of your income are taxed at different rates. Only the income within each bracket is taxed at that bracket's rate.

4. Using the Calculator

Tips: Enter your taxable income in dollars and select your filing status. The calculator will estimate your federal income tax and FICA contributions.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between marginal and effective tax rate?
A: Marginal rate is the tax on your next dollar of income, while effective rate is your total tax divided by total income.

Q2: Are state taxes included in this calculator?
A: No, this only calculates federal income tax and FICA. State taxes vary by location.

Q3: What is the Social Security wage base limit?
A: For 2023, Social Security tax applies only to the first $160,200 of wages.

Q4: How often are tax brackets adjusted?
A: Tax brackets are typically adjusted annually for inflation.

Q5: What deductions are not accounted for here?
A: This calculator assumes standard deduction. Itemized deductions, credits, and other factors would affect actual tax liability.