A small site
that shows its working.

Type a loan amount into most calculators and you get a monthly payment in large type, a chart, and no way to tell whether the figure is right. Was interest compounded monthly or daily? Was the rate divided by twelve or converted properly? Does the total include the rounding on the final payment, or was the whole schedule extrapolated from one rounded figure? These are not pedantic questions — they are the difference between a total that is accurate and one that is out by hundreds of dollars.

The answer is almost never on the page, because publishing it invites someone to check. So the working assumption here is the opposite one: state the formula, name the file it lives in, print the schedule, and list what the tool ignores. A figure you can verify is worth more than a figure presented confidently.

All 15 calculators publish a formula, their assumptions, what they do not model, and the sources behind any rule they encode.

The second reason is narrower. Rules about money are written down, and most sites paraphrase them from each other until the original meaning is gone. The "28/36 rule" gets quoted as though it were law; it is not, and no statute contains it. So where a threshold comes from regulation, this site cites the regulation, and where it is only industry habit, it says that instead. That distinction is worked through on how we calculate.

Rate & Sum is an independent publication. It is not owned by a lender, a broker, a bank, an insurer or a comparison marketplace, and nobody pays to appear on it.

What it does not have is a named financial expert, and the reason is worth being direct about. Pages like this one routinely introduce a team of certified advisers, a founder with two decades in the industry, and a review board. Those claims are unverifiable by a reader and, on a great many sites, untrue. There is no credential here to cite, so none is cited: the publisher stands as the author in this page's structured data, which is the accurate description.

That cuts both ways, and it is the reason the disclaimer matters. Nothing here is financial, tax or legal advice, nobody here is regulated to give it, and a correct calculation is still not a recommendation about your circumstances.

What stands in place of a credential is the audit trail. Every rule is cited to its source with the date it was checked; every formula is testable and tested; every figure the site states about itself is computed rather than typed. You are not being asked to trust a biography. You are being handed the working.

The arithmetic is verified against values computed independently of the code that implements it — worked by hand, or taken from a regulator's own published example — rather than against whatever the code happened to return the first time. A test that records the current output proves only that nothing changed; it cannot tell you the output was ever right.

The suite covers more than the maths. It also checks the things a content site gets wrong quietly: that no internal link points at a page that does not exist, that no unpublished page leaks into the sitemap, that structured data describes something actually visible on the page, and that the claims these trust pages make are still true of the code.

That last category is unusual and it is deliberate. A sentence on this page saying there are no affiliate links is worth nothing on its own. A test that searches the source for affiliate, sponsored and referral markers, and fails the build if one appears, turns the sentence into something you can rely on. The verification approach is set out in full on how we calculate.

Some things a test cannot do. Keyboard-only navigation, screen-reader output, print layout and performance under a real network have not yet been checked by hand on these pages, and this sentence stays here until they have been.

The site covers these areas today:

• Mortgage & Home — Work out payments, affordability, amortisation and the cost of paying early.
• Loans & Debt — Payments, interest, amortisation and payoff strategies for any fixed-rate loan.
• Saving & Investing — Compound growth, contributions, returns, inflation and goal planning.
• Salary & Pay — Convert pay periods, compute overtime, raises and take-home pay.
• Business — Margins, markup, break-even, ROI and business financing.
• Everyday Money — Percentages, discounts, budgets, savings goals, net worth and inflation.

3 further categories are planned and are declared in the site's own content model, but none of them holds a published tool, so none appears in the navigation. An empty category page is a thin page, and a link to one is a dead end on every page that carries the menu.

This is the growth rule, and it is the one most likely to be broken later, so it is written down: a page is published when it answers a question a reader actually has, with arithmetic that has been checked. Not when a keyword has search volume. A hundred pages generated to occupy search results would be a different site, and a worse one.

Tools are built against tested maths first and given a page second. Several engines are written and passing tests while their pages are unwritten, which is why the count above is smaller than it will be — and why no half-finished tool is reachable in the meantime.

Comparison sites are usually paid per click or per completed application, which shapes everything above it: which lenders appear, in what order, and how insistently you are pushed toward an enquiry form. That model is not in use here. There are no affiliate links, no sponsored or paid placements, no referral arrangements, and no lead generation of any kind — the site has nothing to sell you and no form that sends your details to anybody.

Display advertising is currently switched off. The site is built so that it stays fully usable if it is ever turned on: every slot reserves its space in advance so nothing shifts as the page loads, and no advert has access to the figures you enter.

Analytics is currently switched off. If it is enabled, it records that a calculator was used and which one — never the values entered, and never the query string that might carry them.

Calculations run in your browser; there is no endpoint they are sent to. There is one case where a URL you open can carry figures in its request line, and the privacy policy sets out exactly what that does and does not cover.

Everything above rests on the arithmetic being right, so an error in it matters more here than it would on a site that never invited you to check. If a figure disagrees with your lender's number, with your own working, or with a source cited on the page, that is a defect and we want to hear about it — with the inputs, so it can be reproduced.

Corrections are made to the calculation first and then to every page that quoted it. Each tool carries the date its formula was last reviewed and a version number that changes when the formula does, so a correction is visible rather than silent. The full process is on the editorial policy page.

Report an error, or ask how a figure was derived, on the contact page.