How the Maths Works

Where the rates come from

Each rate is taken from the government tax authority that sets it. No estimates, no second-hand compilations, nothing crowd-sourced. The data file behind every country carries a direct link to the page it was read from, so the chain is checkable.

Those sources get revisited when a tax year turns, and straight away if a government announces a change partway through one.

What the calculators count

Everything an ordinary employee sees taken off a payslip:

Income tax, worked through the progressive bands along with any personal allowance or basic deduction
Social insurance, meaning the employee share going to state pension, unemployment cover and health funds
Solidarity surcharges, where a country still levies one, as Germany does at the top end
Health levies, such as the Australian Medicare Levy or the US Medicare component of FICA

What is deliberately left out

Some deductions swing so far between individuals that including them by default would make the answer less accurate, not more:

Workplace pension contributions, which depend on the scheme and on what you chose
Student loan repayments, which vary by plan and by country
US state and local income taxes, anywhere from nothing to over 13%
Canadian provincial income tax, which differs sharply between provinces
Swiss cantonal and communal tax, where the canton matters more than the federal rate
Church tax in Germany and Austria, which only applies if you are registered
Benefits in kind such as a company car or private medical cover
Reliefs and credits that hang on personal circumstances

Any of these will move your real figure away from the one shown. What you see is a standard full-time employee with nothing beyond the deductions and reliefs that apply to everyone.

The method itself

Income tax runs through each country's own bracket structure. The tax due on the slice of income sitting inside each band is worked out separately, then the slices are added up. This is the same way the authorities do it, which matters because a flat average across the whole salary gives the wrong answer.

The UK for 2026/27, as an example:

The first £12,570 attracts nothing, being the Personal Allowance
£12,571 to £50,270 is charged at 20%
£50,271 to £125,140 at 40%
Anything above £125,140 at 45%

National Insurance and the equivalent social contributions elsewhere are handled on their own, since they run on separate thresholds that rarely line up with the income tax bands.

A few countries, Germany among them, set tax by a continuous formula rather than by bands. Those are approximated with band averages, which lands within 1% to 3% of the true figure across most of the income range. The calculators concerned say so on the page.

Effective rate against marginal rate

The effective rate is total tax divided by gross income, expressed as a percentage. It is the average across everything you earned, and it is always lower than your top band.

The marginal rate is what the next unit of currency would be taxed at. That is the number worth knowing before taking on extra hours or weighing up a rise, because it tells you what the raise is actually worth.

When things get updated

Once a tax year: every one of the 22 countries is reviewed as its own year begins.
Out of cycle: budget announcements and emergency legislation are applied within 48 hours of official publication.
Reader reports: a confirmed error is corrected within 48 hours of being verified.

Each data file carries a lastUpdated and a nextReview date. Both are visible in the admin panel and readable straight from the JSON at /data/tax-rates/[country].json.

The necessary caveat

What this site produces are estimates published for general information. They are not financial or tax advice, and no calculator can be. Before anything turns on the number, check it against the official source or put it to a qualified tax professional.