Question 1

How is federal income tax calculated?

Accepted Answer

The IRS uses a progressive bracket system: each portion of your taxable income is taxed at the rate for that bracket, not your whole income at your top rate. Your taxable income is your gross income minus deductions and pre-tax contributions like a 401(k) or HSA.

Question 2

What's the difference between marginal and effective tax rate?

Accepted Answer

Your marginal rate is the rate applied to your next dollar of income — the rate of the highest bracket you reach. Your effective rate is your total tax divided by your income, blending all the lower brackets you passed through along the way. Effective rate is always lower than, or equal to, your marginal rate.

Question 3

Should I take the standard deduction or itemize?

Accepted Answer

Take whichever is larger. The 2024 standard deduction is $14,600 for single filers or $29,200 for married filing jointly; itemizing only helps if your deductible expenses — mortgage interest, state and local taxes (capped at $10,000), charitable gifts, and qualifying medical expenses — add up to more than that.

Question 4

How does a 401(k) contribution lower my taxes?

Accepted Answer

Traditional 401(k) contributions are deducted from your paycheck before federal (and most state) income tax is calculated, directly reducing your taxable income. They're still subject to Social Security and Medicare tax, though — only the income tax portion is deferred until you withdraw the money in retirement.

Question 5

What is an HSA and how does it reduce taxable income?

Accepted Answer

A Health Savings Account lets people enrolled in a qualifying high-deductible health plan set aside pre-tax money for medical expenses. HSA payroll contributions reduce your taxable income for federal income tax and are also exempt from Social Security and Medicare tax — a rare triple tax advantage.

Question 6

Which states have no income tax?

Accepted Answer

Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming don't tax wage income. New Hampshire does tax some interest and dividend income separately. Every other state, plus Washington, D.C., levies some form of income tax.

Question 7

What is FICA and who pays it?

Accepted Answer

FICA stands for the Federal Insurance Contributions Act — the payroll tax that funds Social Security (6.2% up to the annual wage base) and Medicare (1.45%, uncapped). Employees and employers each pay half; this calculator shows only the employee's share withheld from your paycheck.

Question 8

What is the Social Security wage base, and why does it matter?

Accepted Answer

The Social Security wage base is the maximum amount of earnings subject to the 6.2% Social Security tax each year — $168,600 in 2024 and $176,100 in 2025. Income above that threshold isn't taxed for Social Security, which is why high earners' effective FICA rate actually drops as their income rises.

Question 9

What is the Additional Medicare Tax?

Accepted Answer

High earners pay an extra 0.9% Medicare tax on wages above $200,000 (single or head of household), $250,000 (married filing jointly), or $125,000 (married filing separately). Unlike the standard 1.45% Medicare tax, this surtax isn't matched by your employer.

Question 10

How accurate is this calculator versus my actual tax return?

Accepted Answer

This calculator models federal and state brackets, the standard deduction, and FICA accurately, but it can't account for tax credits like the Child Tax Credit or Earned Income Tax Credit, other income types, or every state's unique deduction rules. Treat it as a solid estimate, not a substitute for tax software or a professional preparer.

US Income Tax Calculator

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