About Calcenta

Who runs this site

Calcenta is published by FJ GROUP, based in Tunis City, Tunisia.

I'm a software developer, and I build Calcenta on my own: the calculators, the explanations behind them, and the tests that keep them honest. If something here is wrong, I'm the person who fixes it.

You can reach us any time through the contact page. We read everything, and corrections are genuinely welcome.

Why this site exists

Search for almost any calculation and you will find dozens of pages that take four inputs, return a single number, and tell you nothing about where it came from. That number might be right. You have no way to know.

The problem is worse when the stakes are high. A mortgage calculator that shows a monthly payment but hides the $408,000 of interest behind it is technically accurate and practically misleading. A calorie calculator that returns a target without mentioning its 10% margin of error invites false precision.

Calcenta takes the opposite approach: show the working. Every calculator here gives you the formula in plain English, a breakdown rather than a lone figure, a worked numeric example you can verify by hand, and an honest statement of what the method cannot account for.

The standard every page has to meet

A calculator does not go live here until all of the following are true:

• The math is tested. Every formula is covered by automated unit tests, including the edge cases that break calculators - zero, negative, empty, and absurdly large inputs. Nothing on this site should ever show you NaN.
• The result is broken down. Not one number, but the components behind it: a payment schedule, a split between principal and interest, a per-goal comparison.
• The explanation is original. Written specifically for that tool, with the formula stated plainly and a worked example using real figures.
• The limits are stated. Where a method is an approximation, or where it stops being reliable, the page says so.

We would rather publish fifteen tools that meet this bar than a hundred that do not. Our methodology page documents the formulas and sources in detail.

How the site is built

Every calculation runs in your browser. Nothing you type - your salary, your debts, your weight, your due date - is ever transmitted to a server. That is a deliberate design decision, not an incidental one: the fastest way to keep sensitive numbers private is never to receive them.

The site is a statically generated Next.js application. Pages are pre-rendered as HTML, so they load fast on slow connections and work correctly on any device.

How this site is funded

Advertising, through Google AdSense, and nothing else. There are no affiliate links, no sponsored placements, no paid rankings, and nothing for sale. No advertiser has ever influenced what a calculator says or how a result is presented, and none ever will - if a result is bad news, the page says so.

Ads are kept off our policy pages entirely, and collapse rather than leaving a blank space when nothing is served. You can turn off advertising cookies from the Manage cookies link in the footer without losing access to anything.

Corrections

If a calculator gives a wrong answer, or an explanation is unclear or out of date, please tell us. Include the tool, the numbers you entered, and what you expected. Errors get fixed quickly, and tax-year figures are reviewed annually.