Health & Body Tools

Calorie & TDEE Calculator opens this category because the question it answers — how many calories do I actually need each day — sits upstream of every other health number. It runs the Mifflin-St Jeor equation, which independent meta-analyses place within 10% of measured resting metabolic rate for most adults, and then multiplies by an activity factor to reach the figure a person needs to maintain their weight. A 30-year-old male at 80 kg and 178 cm exercising moderately lands at 2,843 kcal per day; the same person sedentary lands at 2,201. That 642-calorie gap is larger than a meal, and it is why two people on identical diets can have opposite results.

BMI Calculator sits alongside it here from the Math & Calc category: enter weight and height in metric or imperial units and it returns the standard WHO classification from Underweight through Obese Class III. The goal table in Calorie & TDEE Calculator then gives the daily targets needed to move that number, so the two tools answer the same question from different angles without duplicating each other.