Income tax calculator (UK and US)
Income tax, National Insurance or FICA and your effective and marginal rates, with the full band breakdown.
About the income tax calculator (uk and us)
Income tax, National Insurance or FICA and your effective and marginal rates, with the full band breakdown.
Part of SmartCalcy’s tax & salary tools. It runs in your browser with no account, uses your own currency and units (change them at the top of the page), and gives estimates for information only, so check official guidance before you rely on a result.
How to use the income tax calculator (uk and us)
What it calculates and when to use it
Estimates income tax, National Insurance (UK) or Social Security and Medicare (US), your effective and marginal rates, and a band-by-band breakdown.
How to use it, step by step
- Choose where you pay tax: England/Wales/Northern Ireland, Scotland or the US.
- Enter your income per year before tax.
- Add pension or 401(k) contributions paid before tax and, in the UK, a student loan plan.
- Read the tax, take-home pay and marginal rate.
What each input means
- Income – Gross pay for the year.
- Filing status (US) – Sets the standard deduction and brackets.
- Pension paid before tax – Reduces taxable income.
- Student loan plan (UK) – Plan thresholds and rates decide repayments.
How to read the results
- Income tax – The sum of tax in each band.
- Effective rate – Income tax ÷ income.
- Marginal rate – Total tax on the next unit of income, including National Insurance or FICA.
- Tax by band – How much was taxed at each rate.
The formula
UK: taxable income = income − personal allowance (12,570, reduced by 1 for every 2 over 100,000). Tax is 20% on the first 37,700 of taxable income, 40% to 125,140 and 45% above in England; Scotland uses six bands. National Insurance is 8% between 12,570 and 50,270 and 2% above. US: taxable income = income − standard deduction, taxed in 10% to 37% brackets.
A worked example
A UK taxpayer earning 50,000 has a personal allowance of 12,570, so 37,430 is taxable at 20% for 7,486 of tax. National Insurance is 2,994, take-home pay is 39,520 and the marginal rate is 28%.
Assumptions and limits
- UK: standard tax code, no other income, no Marriage Allowance or benefits.
- US: federal tax only with the standard deduction. State taxes, credits and itemised deductions are excluded.
- Pension contributions are treated as paid before tax but not before NI.
Common mistakes
- Applying the top rate to all income. Only income in each band is taxed at that band’s rate.
- Forgetting National Insurance or FICA.
Frequently asked questions
Why is my marginal rate 60% between 100,000 and 125,140 in the UK?
The personal allowance is withdrawn as income rises, so each extra pound is taxed at 40% plus the lost allowance, an effective 60% before NI.
Does Scotland have different rates?
Yes. Scotland sets its own bands and rates for non-savings income. Choose Scotland to see them.
Dated rules: UK tax year 2026 to 2027 (6 April 2026 to 5 April 2027), from GOV.UK. Rates and thresholds change each year, so check GOV.UK before relying on a figure. Dated rules: US federal figures for tax year 2026 (IRS Rev. Proc. 2025-32 and IRS notices). These calculators are estimates for planning, not tax advice.
Related tools
Details
- Personal allowance
- £12,570
- Taxable income
- £37,430
- National Insurance
- £2,994
- Total tax and deductions
- £10,48021% of income
- Effective tax rate (income tax only)
- 15%
- Marginal rate on your next pound
- 28%income tax plus deductions on extra pay
- Take-home per year
- £39,520
Tax by band
| Band | Rate | Tax |
|---|---|---|
| £0 to £37,430 | 20% | £7,486 |