Income Tax Calculator
Calculate income tax owed, effective rate, marginal rate and a full bracket breakdown for the US or UK.
Source: HMRC Income Tax rates and Personal Allowances; IRS Revenue Procedure 2025-32 · UK 2026/27, US 2026 · last verified 2026-09-12
How this is calculated
Income tax is progressive: each bracket's rate only applies to the slice of income within that bracket, not your whole income. For the US, this uses 2026 IRS federal brackets for single and married-filing-jointly filers. For the UK, it applies the 2026/27 personal allowance, basic rate, higher rate and additional rate bands — including the personal allowance taper that phases out the tax-free allowance between £100,000 and £125,140 of income.
Because tax is progressive, your effective rate — total tax divided by total income — is always lower than your marginal rate, since only the income inside each higher bracket is taxed at that bracket's rate. That distinction matters most when deciding whether extra income (a bonus, overtime, or a pension contribution) is worth it: the relevant comparison is always the marginal rate on that next slice of income, not your overall effective rate. To see your take-home pay across different pay periods once tax is accounted for, see the Salary calculator, and to see how pension contributions affect your long-term position, see the Retirement Savings calculator.
Frequently asked questions
- Is this gross income or taxable income?
- Enter your gross income. For the US this is your income before the standard deduction; the bracket calculation here applies rates directly to the amount you enter. For the UK, your personal allowance (the first slice of income taxed at 0%) is applied automatically, including the taper that reduces it to zero between £100,000 and £125,140.
- What's the difference between effective rate and marginal rate?
- Your effective rate is total tax owed divided by total income — the average rate you actually pay. Your marginal rate is the rate on your next pound or dollar earned, which is usually higher than your effective rate because only income above each threshold is taxed at that threshold's rate.
- Why can the UK marginal rate hit 60%?
- Between £100,000 and £125,140 of income, the UK's personal allowance is withdrawn at £1 for every £2 earned. That withdrawn allowance itself becomes taxable at 40%, so an extra £1 of income there costs you 40p of direct tax plus another 20p from the shrinking allowance — a 60% effective marginal rate, well known as the UK's '60% tax trap'.
- Does this include state, local, or National Insurance contributions?
- No — this covers US federal income tax and UK income tax only. It does not include US state/local income tax, or UK National Insurance contributions, both of which are calculated separately and vary by state or circumstance.
- Can I use this in my own app?
- Yes — every calculator on Stupidly Clever has a matching REST API and MCP tool that runs the same underlying logic.
- What is the difference between marginal and effective tax rate?
- The marginal rate is the rate applied to your last pound/dollar of income — the rate in your highest bracket. The effective rate is total tax divided by total income — always lower than the marginal rate because lower income is taxed at lower brackets. Decisions about extra work, bonuses, or pension contributions should use the marginal rate.
- What is fiscal drag, and does it affect me?
- Fiscal drag occurs when tax thresholds are frozen while incomes rise with inflation, pulling more taxpayers into higher brackets without any real increase in purchasing power. If your income has risen with inflation but the tax-free allowance and bracket thresholds have not moved, you are experiencing fiscal drag.