What is your BMI?
Enter weight and height to see your range instantly — with the full WHO table and what to do from there.
Educational content based on WHO guidelines and scientific literature. Not a substitute for individual medical or nutritional advice.
| BMI (kg/m²) | Classification | What it usually indicates |
|---|---|---|
| Below 18.5 | Underweight | Low energy reserves; investigate causes and prioritize muscle gain |
| 18.5 – 24.9 | Healthy weight | Lowest statistical risk of weight-related disease |
| 25.0 – 29.9 | Overweight | Increased risk; moderate calorie deficit plus strength training |
| 30.0 – 34.9 | Obesity class I | High risk; structured routine change, ideally with professional support |
| 35.0 – 39.9 | Obesity class II | Very high risk; professional follow-up recommended |
| 40.0 or more | Obesity class III | Extreme risk; medical supervision is essential |
What BMI is and how it is calculated
BMI (Body Mass Index) is the world’s most used screening measure for whether weight matches height. The formula is simple: weight divided by height squared — BMI = weight (kg) ÷ height² (m). Someone at 80 kg and 1.75 m has a BMI of 80 ÷ (1.75 × 1.75) = 26.1, which lands in the overweight range.
Created in the 19th century by mathematician Adolphe Quetelet and adopted by the World Health Organization as a population standard, BMI earned its place for a practical reason: it needs only two numbers everyone knows by heart, and still points in the right direction for the vast majority of people.
The calculator above runs that math instantly and places your result on the WHO scale — from underweight to obesity class III — so you see not just the number but the distance to the healthy range.
What your result means in practice
Below 18.5, the body usually carries low energy reserves and muscle mass — the path typically involves a moderate calorie surplus and strength training, not just "eating more junk". Between 18.5 and 24.9 sits the range associated with the lowest risk of type 2 diabetes, hypertension and cardiovascular disease in large population studies.
From 25 to 29.9 (overweight), metabolic risk starts climbing — but it is also the range where response to training and a calorie deficit tends to be fastest and most visible. Above 30, the WHO splits obesity into three classes, and from class II onward professional follow-up stops being a suggestion and becomes a need.
One detail rarely explained: BMI is a starting point, not a sentence. Two people at BMI 27 may need opposite strategies — one carrying abdominal fat, the other carrying muscle. That is why the next numbers to look at are body composition and waist circumference.
BMI’s limitations (read before you panic)
BMI cannot tell muscle from fat. Trained people often read "overweight" while lean — and sedentary people can hold a "healthy" BMI while carrying too much visceral fat, the so-called "skinny fat" profile.
- Does not distinguish muscle mass from body fat
- Does not show where fat is stored (abdominal fat carries the highest risk)
- Not valid for children and teens — they use age- and sex-specific percentile curves
- Underestimates risk in older adults, who naturally lose muscle with age
- Ignores differences in frame size and ethnicity
How to leave the overweight range (without crash diets)
Lowering BMI is the same math as losing fat: burn more than you eat, with a 300–500 kcal daily deficit, high protein (1.6–2.2 g per kg) to preserve muscle, and strength training 3–5 times a week. At that pace you lose 0.5–1% of body weight per week — for a 90 kg person, 2–4 kg per month, sustainably and without rebound.
That is exactly the math ShapeLeague runs in the quiz: your BMI goes in as the starting point, and out come daily calories, macros and a 28-day training plan calibrated to your level. Use the calorie calculator below to see the next number in your journey.
Reviewed July 2026
Frequently asked questions
How do I calculate BMI manually?
Divide your weight in kilograms by your height in meters squared: BMI = weight ÷ (height × height). Example: 70 kg at 1.68 m → 70 ÷ (1.68 × 1.68) = 24.8.
What is the ideal BMI?
The WHO healthy range runs from 18.5 to 24.9 kg/m². Within it, "ideal" depends on body composition, age and history — two bodies at the same BMI can look very different.
Does a high BMI mean I’m fat?
Not necessarily. BMI can’t tell muscle from fat: athletes often read overweight with low body fat. Use it as screening and confirm with body fat percentage and waist circumference.
What BMI counts as obesity?
From 30 kg/m² upward. The WHO splits it into class I (30–34.9), class II (35–39.9) and class III (40+), with rising metabolic and cardiovascular risk.
Is the formula the same for men and women?
Yes — the formula and WHO ranges are identical for adults of both sexes. Sex differences in composition show up in complementary measures like body fat percentage.
Does BMI work for children and teens?
Not with this table. Under-18s use age- and sex-specific percentile curves, assessed by a pediatrician.
How do I lower BMI in a healthy way?
Moderate calorie deficit (300–500 kcal below expenditure), high protein to preserve muscle, and strength training 3–5 times a week. Sustainable pace: 0.5–1% of body weight per week.
What’s the difference between BMI and body fat percentage?
BMI relates weight to height; body fat percentage measures how much of that weight is actually fat. BMI is quick screening; body fat is the true picture of composition.
Now turn that number into a plan
The quiz uses these same formulas — plus your real routine — to build training and diet your way. Takes 60 seconds.
Build my free plan →