How we verify the math

A calculator that returns a confident wrong answer is worse than no calculator at all, because it costs you the chance to catch the mistake yourself. Everything on CalcGauge is built with that in mind. This page describes how each tool is put together and checked, so you can decide how far to trust it.

Every formula comes from a published source

None of the math here is invented. Loan and mortgage payments use the standard amortization formula, the one where a fixed monthly payment is the principal times the monthly rate times a compounding factor, solved so the balance reaches zero on the final payment. Body Mass Index uses its actual definition, weight in kilograms divided by height in metres squared, with the familiar imperial version carrying the 703 conversion constant baked in. Percentage change, compound interest, date differences, unit conversions: each one traces back to a definition you could look up and confirm. Where a field has more than one accepted convention, such as how age is counted across a leap day or which day a week is considered to start on, the tool page says which one it uses.

Each calculator is checked against a separate calculation

Writing a formula into a web page and having it produce the right answer are two different things. An off-by-one in a loop, a rounding step in the wrong place, a unit assumed rather than stated: any of these can pass a casual glance and still be wrong. So before a calculator goes live, its output is compared against the same problem worked a second way, independently, usually in a short script written from the formula rather than copied from the page. When the loan calculator says a thirty-year mortgage pays a certain amount of total interest, that figure was reproduced by a separate amortization run built for the check. If the two disagree, the tool does not ship until they agree and the reason is understood.

The worked example on each page is real

Most calculator pages here include a worked example with specific numbers. Those numbers are not decorative. They are run through the same verification, so the example doubles as a test you can repeat: put the stated inputs into the tool and you should get the stated result. If you ever find a page where the worked example and the live calculator disagree, that is a genuine bug, and the contact form is the fastest way to get it fixed.

Rounding is disclosed, not hidden

Money is rounded to the cent, and where a result depends on how intermediate values are rounded, the page says so. A mortgage lender may apply an extra payment on a slightly different schedule than a general calculator assumes, and a currency or unit conversion is only as current as the rate you feed it. These limits are stated on the individual tool pages rather than buried, because the honest version of a calculator tells you where its answer stops being exact.

What runs where

The calculations happen in your browser, in JavaScript, on your device. Numbers you type into a loan or salary or health calculator are not sent to a server, because there is no server-side calculation to send them to. That keeps the tools fast and keeps your figures private. It also means results should be sanity-checked when a real decision rides on them: treat these as a fast, transparent second opinion, not as financial, medical, or legal advice.