How we review

Every calculator on this site is drafted from cited primary sources and checked by automated tests, under human supervision. No page is written, edited, or personally signed off by a named human expert. A credit such as "Editorial Team" names a role, not a person: inventing a name or a credential would be a false trust signal, and we would rather tell you what is missing.

How a number gets onto a page

The formula comes from a published source, and every constant in it has to appear word for word in a quoted passage from that source — nothing is used from memory. Two independent attempts then implement the formula from those quotations alone, and they must agree with each other and with the source's own published values before either one is used. The page's structure and its arithmetic are assembled by code from there; a model writes only the explanation around them, and a different model checks every sentence of that explanation back against the same quotations.

What's checked before a calculator publishes

A page publishes only when all 13 of these checks pass, unattended, on the same frozen version of the page. Each line below is what the check gets you, followed by what it actually measures.

The number the reader gets is right.two independent implementations agree with each other and with the authority.
The arithmetic is sourced, not remembered.every formula constant appears verbatim in a quoted authority excerpt.
No figure on the page is invented.every number in the article is an input default, an authority value, or a reproduced example.
Every claim can be checked by following a link.every citation resolves to a captured source with URL and access date.
The page is not padded; the reader is never told the same thing twice.no passage of twelve or more words is repeated anywhere on the page.
A general reader can follow the explanation.reading level: Flesch-Kincaid grade at most 10 for the article body.
The page is at least as broad as the best one a reader could land on instead.topic coverage is a superset of the top three competitors' section topics.
Every statement on the page is true to its source.a different model family finds no claim unsupported by the excerpts.
The page is fast and usable on a phone and with a screen reader.Lighthouse at least 95 in all four categories on mobile, zero axe violations.
Search engines and answer engines can read and cite the page.structured data validates.
Outside the formula's limits the reader sees an honest message, never a wrong number.validity domain is stated on the page and enforced by the calculator.
The reader can see who stands behind the page and that no expert review is being faked.author, methodology link, sources list and last-reviewed date present; reviewer null shown as such.
The reader sees the formula the page computes with, not just its result.the built page shows its formula block.

Where a new page replaces an earlier version at the same address, it must also beat that version in a side-by-side judgement of breadth, accuracy, clarity and honesty, made by a model family that wrote neither page and asked twice with the pages swapped.

What we don't claim

None of this substitutes for a named human expert reviewing a page — it substitutes for nobody reviewing it at all. These checks can confirm that a number matches its source, that every figure on the page can be traced back to one, and that nothing is asserted the sources do not support. They cannot tell you whether the source is the right one for your situation, or whether a formula that is correct in general suits your particular case.

Where a calculator deals with money or health, the page says so about itself: itnames the credential a reviewer of that subject would need, and states plainly that nobody holding it has signed the page. If that changes, the page shows the reviewer's name, their credential, and the date they signed — and until it does, it will not pretend otherwise.

Found something wrong?

If a number looks off, a source is broken, or anything else here is wrong, report it — it opens a short form that reaches the operator directly.