Knowledge base
Formulas, sources, and the science behind every calculator
Every calculator on this site cites its formula. These guides explain where each formula comes from, when it's most accurate, and where it falls short.
How to Track Calories Accurately
A 5-step practical guide. Most people under-report intake by 20–40%; this fixes it.
Read the guideThe Mifflin–St Jeor Equation
Why dietitians use Mifflin–St Jeor over Harris–Benedict for BMR estimation.
Read the guideThe Harris–Benedict Equation
The original 1919 BMR equation and the 1984 Roza–Shizgal revision.
Read the guideThe BMI Formula Explained
Where Body Mass Index comes from and where it breaks down.
Read the guideActivity Multipliers (PAL)
How to pick a TDEE activity multiplier honestly — most people overshoot.
Read the guideProtein Requirements
Evidence-based daily protein intakes from ISSN, ACSM, and Morton 2018 meta-analysis.
Read the guideMacronutrients 101
Protein, carbs, and fat — calories per gram and how to split them.
Read the guide