What this site is
A set of calculators for the money questions that come with a salary, a border or a loan. What a gross salary leaves after tax in a given country or US state. What that net figure is worth once the price level where you would live is taken into account. What a mortgage or a personal loan actually costs, month by month. Which debt to clear first, and what the order is worth. What a stream of payments is worth today.
Every calculator is its own page. Each one works without JavaScript, answers on the first load, and asks for nothing: no account, no sign-up, no saved history. None of those would make an answer arrive faster, and each of them would be one more thing holding a number that is nobody's business but yours.
Two kinds of calculator, held to two standards
The tools here split in two, and the honest standard is different for each.
Statutory tools apply rules somebody published: income tax bands, social insurance ceilings, student loan thresholds, withholding tables. Every figure in one of those traces to an official document from a revenue service or a state department of revenue. The page names the document, the tax year it applies to, and the date the data file was last checked against it. Nothing is written from memory, and nothing is copied from another calculator.
Formula tools apply arithmetic that is nobody's rule: a loan payment, compound growth, an internal rate of return, a margin, a deposit. There is no authority to cite for those, so the page owes you the other thing instead. It states the formula it used, the convention it picked where more than one is defensible, and what it deliberately leaves out. A payment computed monthly in arrears is a different number from one computed in advance, and a calculator that will not say which it did is asking to be trusted rather than checked.
How the numbers are kept honest
Tax rules live in dated data files, one per jurisdiction per tax year, each carrying the source document it was read from and the date somebody last checked it against that document. Changing a rate means changing a file, and the year it replaces stays where it is, so a calculation made against an earlier year can still be reproduced.
The same rules are implemented twice, once on the server and once in the browser, and both are run against the same fixtures taken from official tables. If the two ever disagreed, the tests would fail before the page could ship. That is the reason a result can change as you type without the arithmetic behind it being loose.
Errors still happen. Law changes mid-year, a threshold moves, a document is superseded, a reading is wrong. Reporting one is the quickest way to have it fixed, and the contact page says what to include so that it can be checked against the source rather than debated.
Who runs it, and how it is paid for
This is an independent site. It is not affiliated with, endorsed by, or operated by any tax authority, bank, lender, broker or employer.
Advertising pays for it. Ads are marked as ads, they are kept out of the space between a form and its answer, and they load only after the page is usable. Nothing on a result page is a paid placement: every figure is computed from what you entered and from the data files, and no result is ranked, filtered or reordered by anyone's commercial interest. Where a page quotes a commercial product's published terms, it says when those terms were collected and stops showing them once they are too old to stand behind.
What this site does not do
It does not give tax, legal or financial advice, and using it creates no professional relationship. It does not know your circumstances: the calculators assume the standard case for a jurisdiction unless you change the options on the page, and a real payslip is shaped by things no calculator is told about. It does not file anything, does not talk to any tax office or lender on your behalf, and has no way to see what you entered.
Treat a figure here as a good estimate for comparing two options. For a decision that turns on the exact amount, check it against the authority that will collect it or the lender that will charge it. The disclaimer page puts the same point at more length, and the privacy policy sets out exactly what happens to what you type.