BMI and body fat percentage explained

The scale shows your total weight but not what it is made of. BMI and body fat percentage tell you a bit more — as long as you know how they are calculated and where they fall short.

Body mass index (BMI)

BMI = weight (kg) ÷ height (m)². In pounds and inches: BMI = 703 × weight (lb) ÷ height (in)². Example: 176 lb at 5′11″ (71 in) → 703 × 176 ÷ 5,041 ≈ 24.5.

WHO categories for adults:

• below 18.5 — underweight;
• 18.5–24.9 — healthy weight;
• 25–29.9 — overweight;
• 30 and above — obesity.

Where BMI falls short

• It cannot tell muscle from fat. A muscular person can be “overweight” by BMI with low body fat.
• It ignores where fat sits. Belly fat is linked to health risks more strongly than fat on the hips and thighs.
• It fits some groups poorly: children and teens (who use BMI-for-age charts), older adults and pregnant women.

BMI is a rough screening tool for most adults, not a diagnosis.

Body fat percentage

Body fat percentage is the share of your weight that is fat tissue. Rough ranges from the American Council on Exercise (ACE):

• Men: 6–13% athletes, 14–17% fitness, 18–24% average, 25%+ obese.
• Women: 14–20% athletes, 21–24% fitness, 25–31% average, 32%+ obese.

Going below essential fat (about 2–5% for men and 10–13% for women) is not healthy either.

How to estimate yours

• Reference photos — compare yourself with pictures of different body fat levels. Rough, but free.
• A BMI-based formula (Deurenberg): 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex = 1 for men and 0 for women. It inherits BMI's blind spots.
• Smart scales (bioimpedance) — swing with hydration, so morning and evening readings differ. Useful for trends if you weigh in under the same conditions.
• Skinfold calipers — accuracy depends on who takes the measurement.
• A DEXA scan — the most accurate widely available method, done at clinics.

Waist size — a simple, useful check

A tape measure sometimes tells you more than the scale. Health risk goes up with a waist over 40 in (102 cm) for men and 35 in (88 cm) for women; the WHO also flags a lower “increased risk” level at 37 in (94 cm) and 31.5 in (80 cm). Another rule of thumb: keep your waist under half your height. Measure in the morning, after breathing out, midway between your lowest rib and the top of your hip bone.

How Temfy Nutri shows it

Your profile in Temfy Nutri has a Body mass index card with a category scale and a short tip. You can enter your body fat yourself (with reference pictures for men and women) — then if your BMI is above the range but your body fat is fine, the app tells you so. If you leave it blank, body fat is estimated from BMI and marked with “≈”.

Profile → Measure keeps your weight and body measurements — neck, shoulders, chest, biceps, waist, hips and thigh — with charts by week, month and year. Height can be in inches and weight in pounds. Changing your weight or body fat in the profile recalculates your calorie targets (see how they are calculated).