About Calcustack

Calcustack is a growing library of free online calculators paired with honest, plain-spoken explanations. We started in 2025 with fitness and nutrition, and we're expanding into finance, math and unit conversion next.

What we do differently

Most calculator sites are either a blank input field with no explanation, or a wall of SEO-optimized fluff hiding the actual tool. We refuse both. Every page on Calcustack puts the calculator first, gives you the result instantly, and follows up with the formula, worked examples, common mistakes, and an FAQ, written by humans who actually use this stuff.

How we make money

Display ads. The site is free and will stay free. Ads are clearly labeled and won't push content around as they load. We never sell your data, most calculations run entirely in your browser and never reach our servers.

Who's behind this

A small team of people who got tired of sketchy calculator sites and decided to build a better one. If you spot an error or want a calculator added, the contact page reaches us directly.

Editorial standards

Formulas are sourced from peer-reviewed literature where applicable (Mifflin-St Jeor, US Navy body fat, Boer LBM, etc). Guides cite their reasoning and acknowledge uncertainty. Nothing on this site is medical advice, see our disclaimer.