Last reviewed: November 2, 2026
Overview
Sixpacks.fit is an independent website that offers free, browser-based fitness calculators. This page explains how we choose what to build, how we research and verify our content, how we test our calculators, and how we handle errors. We believe in being transparent about what we do and, just as importantly, what we do not do.
What We Publish
Our content consists primarily of fitness and health calculators. These are interactive tools that run entirely in your browser using JavaScript. We currently offer 12 free tools: calculators for body fat percentage, daily calorie needs, macro targets, BMI, and other common fitness metrics, plus an abs workout generator, a workout timer, and a Summer Preparation Planner. Each calculator is based on a published, publicly available formula or methodology. We also publish informational articles related to fitness, nutrition, and body composition to help users understand what the numbers mean and how to interpret them.
We do not provide medical advice, diagnosis, or treatment recommendations. Our calculators produce estimates, not clinical measurements. Always consult a qualified healthcare professional for advice specific to your situation.
Topic Selection
We choose what to build based on what people are actually looking for. Common fitness questions like "How much body fat do I have?" or "How many calories should I eat?" are the kinds of problems our calculators aim to address. We pay attention to user feedback and gaps in existing free tools. If a formula is well-established and widely used but no free, easy-to-use calculator exists for it, that is a candidate for us to build.
Research and Sources
Every calculator we build is intended to be based on a published formula or methodology from a recognizable source. Examples include the U.S. Navy body-fat circumference method, the Mifflin-St Jeor equation for estimating resting metabolic rate, and standard BMI calculations from the CDC and WHO. When we write accompanying articles or explanations, we rely on publicly available information from organizations such as the Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), the National Institutes of Health (NIH), and peer-reviewed research.
We have made calculation errors in the past (for example, incorrect formula constants and mismatched worked examples). Those errors have been corrected, and the affected pages carry update notes. A published source does not by itself guarantee that an implementation is correct, which is why the testing section below matters.
Formula Implementation and Verification
When we implement or revise a calculator, we:
- Identify the source formula and its intended population and units.
- Implement it in JavaScript so it runs client-side, in your browser; no calculator input is sent to a server by the tool itself.
- Test with representative inputs, boundary values, invalid inputs, metric-imperial equivalence, and recalculation after changing units.
- Check that the result, the deficit or loss rate, any timeline, and any worked example printed on the page all agree with one another.
The actual test cases, expected values computed independently from the published formulas, and the results are maintained in the site's test record and summarized on the How We Test Every Sixpacks.fit Calculator page.
If a calculator cannot be made dependable, it is taken down or marked as under maintenance rather than left showing potentially wrong results.
Review
Content is reviewed by the site operator (Shakeel Ahmed) before it goes live, not by licensed physicians or registered dietitians. The site does not have a medical review board. The author is not a doctor, dietitian, or personal trainer, and this is stated plainly on the About page. Where a page addresses injury, pregnancy, postpartum recovery, or a medical condition, it is narrowed to general education and referral guidance rather than prescriptive advice.
Corrections
If we discover an error in a calculator or in our content, we fix it as quickly as possible. Confirmed errors are corrected, and pages that changed carry an update note. When a correction changes a number that users may have relied on, we say so on the affected page. Previous results from a corrected calculator should be recalculated rather than reused.
Use of Automated Writing Tools
[NEEDS SOURCE] — Whether any article or tool text on this site was drafted with the assistance of AI writing tools has not been confirmed by the publisher. If AI-assisted drafting is used, it will be disclosed here and on the affected pages.
Contact
If you spot an error, a broken link, or a number that looks wrong, email team.sixpacks.fit@gmail.com or use the contact page.