Below is a summary of the primary formulas and public health references behind our calculators. We link directly to the original or most authoritative source where possible.
| Calculator | Formula / Reference |
|---|---|
| BMI Calculator | WHO / CDC BMI classification — WHO, CDC |
| Calorie & TDEE Calculator | Mifflin-St Jeor equation; energy planning consistent with the NIH Body Weight Planner |
| Body Fat % Calculator | U.S. Navy circumference method |
| Ideal Weight Calculator | Devine and Hamwi formulas, plus WHO/CDC healthy BMI range |
| Heart Rate Zone Calculator | 220-minus-age max heart rate estimate; zone ranges aligned with American Heart Association guidance |
| Water Intake Calculator | Weight- and activity-based hydration guidance consistent with National Academies dietary reference intakes for water |
| Macro Split Calculator | Acceptable Macronutrient Distribution Ranges (AMDR), Dietary Guidelines for Americans (USDA/HHS) |
| Sleep Cycle Calculator | ~90-minute sleep cycle model; sleep duration guidance from NHLBI and CDC |
| Pregnancy Due Date Calculator | Naegele's Rule, adjusted for cycle length |
| Ovulation Calculator | Standard luteal phase estimate (ovulation ~14 days before next period) |
These are population-level, publicly documented formulas used widely in clinical and public health practice. They're a solid, evidence-based starting point — not a personalized medical assessment. For guidance specific to your own health, please consult a qualified healthcare provider.
Spotted an outdated reference or have a source to suggest? Let us know.