About this site
Seventy free calculators, built to give a correct answer and explain how it got there.
What this site is
MarsCalc Hub is a collection of seventy calculators covering finance, health, pregnancy, zakat, maths and science, dates, and student grades. Every tool runs entirely in your browser. Nothing you type is uploaded, stored or transmitted anywhere — which matters when the numbers involved are your salary, your weight or your medical dates.
Why we built it
Most calculator sites give you a number and nothing else. We think the working matters as much as the answer: which formula was used, what assumptions it makes, and where it stops being reliable. So each tool names its formula, shows intermediate values, and says plainly when a result is an estimate rather than a fact.
Where several accepted methods exist, we show them side by side instead of silently picking one. The ideal weight calculator gives you all four formulas because they genuinely disagree. The zakat tools for crops and livestock show the Hanafi and Shafi'i positions together because the schools differ. The SGPA converter shows three formulas because universities do not agree on one.
How the calculators are checked
Every calculator's maths is written as a standalone function and tested against known-correct values before the page is built. Mortgage payments are checked to the cent against published amortisation figures; molar masses against IUPAC atomic weights; Hijri conversions against known calendar anchors and a round-trip test across thousands of dates. Where a tool relies on reference data we do not control — such as growth charts — we say so on the page.
What we do not do
We do not give medical, financial, legal or religious advice. Several of these tools touch subjects where a wrong answer matters: pregnancy dates, calorie targets, zakat obligations. They are calculation aids. For anything consequential, check the result with a professional who knows your situation.
How the site is funded
The site is free and supported by advertising. Ads are kept away from calculate buttons and input fields so they cannot be clicked by accident. We do not accept payment to alter a calculation or to favour a particular formula.
Corrections
If you find a calculator that gives a wrong answer, please tell us and include the numbers you entered. Correctness is the whole point of the site, and a specific reproducible example is the fastest route to a fix. Use the contact page.
This page was last reviewed on 11 August 2026.