Editorial Policy · ILoveCALCS
How we build and
check our calculators.
This page explains where the numbers come from, how the calculation code is checked, how often finance and tax figures are reviewed, how AI is used, and what to do if you find a mistake. It also says where the process falls short. “We” here means NREX Group, the small team that runs the site, described on the About page.
Policy
Sourcing.
A figure or rule should come from the body that sets it, not from an article about it. Where a primary source exists, the calculator is built from it and the page should link to it. This is the order of preference by topic:
| Topic | Source preferred |
|---|---|
| U.S. federal tax | IRS publications, form instructions, and Revenue Procedures |
| Social Security | Social Security Administration (including its POMS manual) and the annual Federal Register notice of cost-of-living and wage-base figures |
| Loans, mortgages, and investing | Consumer Financial Protection Bureau (CFPB) and investor.gov |
| Health formulas and cut-offs | CDC, WHO, and the professional body for the topic, such as ACOG for pregnancy dating |
| Inflation | Bureau of Labor Statistics Consumer Price Index |
| Units and physical constants | NIST |
| Game and puzzle rules | The rules published by the game's owner, plus published mathematics where a solver relies on it |
Three rules follow from that. The wording on each page is original: formulas and facts are not anyone's text, but sentences are not copied from other sites. Where sources disagree, or a rule is open to interpretation, the page states the assumption it makes. And no page claims to be official. This is not a government site, and it has no affiliation with the IRS, the SSA, the CFPB, or any other body named here.
Sourcing is uneven today. Many finance, tax, and health pages link their source at the foot of the page. Most math, physics, and solver pages do not link one yet, and adding sources there is ongoing work.
How formulas are verified.
No single check catches everything, so there are several, and each one has limits.
Math lives in its own module
Each calculator's math sits in a code module apart from the page layout, so it can be tested without the interface and the form and the tests call the same functions.
Reference values from the source
Where the source publishes worked examples, the tests reproduce them. The Social Security benefits tax calculator is tested against the four worked examples and the Worksheet A example in IRS Publication 915, and against the dollar amounts on either side of each threshold, such as $24,999, $25,000, and $25,001 for a single filer.
Independent methods for solvers
A solver is trusted only once it agrees with a method that shares no code with it. The Lights Out solver uses linear algebra over GF(2). Its tests compare it with a brute-force table of all 33,554,432 (225) press combinations on the 5×5 board, and with a row-by-row method on every size from 3×3 to 9×9. The published nullity values (Anderson and Feil, Mathematics Magazine, 1998, and OEIS A159257) are checked too. The KenKen solver is compared with brute force on 150 random puzzles and 150 altered ones, including puzzles with no solution. The Killer Sudoku solver is compared with brute force on 150 puzzles.
Bad input
Tests also feed in empty, negative, non-numeric, and absurdly large values, and check that the tool returns a finite answer or a clear message instead of crashing or showing NaN.
Project-wide checks
Code changes are type-checked, and a catalog script confirms that every listed tool resolves to a working page and that related-tool links point at live pages. These checks guard against broken pages and links. They do not test the math.
What this does not prove
- Not every calculator has automated tests. The tests cover a minority of the tools, mostly the puzzle solvers and recently added tax and finance calculators, and the test scripts are not published on this site.
- A passing test shows that the code matches a reference value or an independent method. It does not show that the reference is the right rule for your situation, or that the rule has not changed since.
- No licensed professional (accountant, clinician, engineer) reviews the pages, and there has been no independent audit. That is why the disclaimers below exist.
How often figures are reviewed.
Tax and benefit figures change on a calendar, so the review follows it.
| Figures | Usually published | What happens |
|---|---|---|
| IRS inflation adjustments (brackets, standard deduction, many limits) | Autumn, before the tax year starts | Affected calculators are updated after the IRS publishes them |
| Social Security cost-of-living adjustment | October, announced by the SSA | Updated, then checked against the Federal Register notice of annual figures when it appears |
| A change in law (a new deduction, a changed threshold) | Any time | The affected page is updated, or states what it does not yet model |
The standard this site holds itself to: calculators that depend on yearly figures are reviewed at least once a year after the new figures are published, and sooner if a law changes the rules. A review compares the figures in the code with the agency's own publication, then updates the figures, the year named on the page, and the review date together. Pages that use yearly figures should name the year they use, so you can tell whether a page is behind.
Calculators that do not depend on yearly figures, such as geometry, physics, and most math, are reviewed when someone reports a problem or when the page is edited. A page's dates change only when its content changes. They are not touched to make a page look fresh.
This is a standard, not a record that every page has been through a full review. The “Last reviewed” date on some finance, health, and business pages is meant to show when the page was last checked against its source. It is not on every page, and a date is not a guarantee that every number was re-verified that day. Older pages are being checked against this standard and not all of them meet it yet. If a page's figure disagrees with the source it names, trust the source and please report the page.
AI assistance.
The calculation code, the explanatory text, the worked examples, the FAQs, and the page titles and descriptions on this site are drafted with AI assistance.
Language models predict plausible text rather than look up facts, so their output is not trusted on its own. That is the reason for the checks above: reference values from the source, independent methods for solvers, and tests for bad input. No page claims to have been reviewed by a licensed expert.
AI is not used to invent people or proof. The site has no made-up authors, reviewer profiles, credentials, testimonials, user reviews, or testing devices, and it will not add any. If a named person ever reviews a page, that page will say who and what they checked.
Reporting an error.
Every calculator page has a Report an issue button near the top. It opens a short form that sends your message to the person who runs the site. You can also use the contact page, or email privacy@ilovecalcs.com, which is the address listed in the Privacy Policy and so is best for privacy and data requests.
The most useful report names the page, the inputs you used, the result you got, the result you expected, and a link to the source if you have one. A confirmed calculation error is fixed in the code, so every page that uses it is corrected together. If the report is about a rule the tool does not model, such as a state tax, the page is updated to say what it leaves out.
Disclaimers.
Every result on this site is an estimate for information and education. It is not professional advice and it is not a quote or an offer. The sitewide footer says so on every page, and the Terms of Service cover the details. Finance, tax, health, and legal pages are meant to carry their own disclaimer as well, written for the type of tool:
- Finance and tax: for planning only, not tax or financial advice. The page names the tax year or law it uses and what it does not model, and points you to a CPA or tax professional.
- Health and fitness: educational, not a substitute for medical advice, diagnosis, or treatment. Results are population-based estimates. Tools that deal with clinical values add that they must not be used to self-diagnose or change medication.
- Legal, insurance, and benefits: not legal advice, not an insurance quote, and not affiliated with the agency that runs the program.
- Game and puzzle solvers: independent tools, not affiliated with or endorsed by the game's owner. Game names are trademarks of their owners and are used only to describe what the tool solves.
- Engineering and safety: estimates, not a substitute for a licensed professional or the applicable code, and not for safety-critical decisions.
Pages do not promise accuracy or outcomes, and they avoid wording such as “guaranteed” or “100% accurate”. The disclaimer rollout is not finished: some older pages, mostly math, utility, and DIY tools, show only the footer line. If you find a finance, health, or safety page without a disclaimer, please report it.