BMI
- Weight relative to height: a quick screen for weight-related health risk.
- Adult bands: under 18.5, 18.5–24.9, 25–29.9, 30 and over.
- Can't tell muscle from fat, or show where fat sits.
Guides
What each number means, and what to do about it.
In depth
The basics
BMR
- Calories your body burns at complete rest — the floor of your daily needs.
- Higher with more muscle and body size; falls with age.
- Multiply by an activity factor (1.2–1.9) to get daily needs (TDEE).
Body fat
- The share of your weight that is fat — a better fitness measure than BMI.
- Fitness range: men 14–17%, women 21–24% (average: 18–24% and 25–31%).
- Tape estimates are within ~3–4% of a DEXA scan.
Calories
- Daily needs = BMR × activity level.
- About 500 kcal a day under that loses ~0.5 kg (1 lb) a week.
- Treat it as a starting point and adjust after 2–3 weeks.
Macros
- Protein and carbs have 4 kcal per gram; fat has 9.
- More protein while losing weight protects muscle.
- Keep fat above ~20% of calories.
Ideal weight
- Four clinical formulas based on height and sex; they disagree by several kg.
- Ignore muscle and frame size — read the result as a rough midpoint.
- A healthy BMI range is the more realistic target.
Water
- Roughly 35 ml per kg of body weight, plus more for exercise and heat.
- All drinks and water-rich food count.
- Pale-yellow urine is the best day-to-day check.
General information, not medical advice. Talk to a doctor about your own health.