Your result will appear here
Fill in the fields and press Calculate.
Body mass index (BMI) reduces where your weight sits relative to your height to a single number: you divide your weight by the square of your height. Used by the World Health Organization, it marks the boundaries between underweight, overweight and obesity — but it is a screening tool, not a diagnosis.
Enter your weight and height, and your BMI, your category, and the healthy weight range for your height appear instantly.
BMI Calculator: step-by-step worked example
- Weight (kg)
- 78
- Height (cm)
- 175
- 1
Convert height to metres
Height (m) = Height (cm) ÷ 100
175 ÷ 100 = 1.75 m
- 2
Square the height
Height² = Height (m) × Height (m)
1.75 × 1.75 = 3.0625 m²
- 3
Body mass index
BMI = Weight ÷ Height²
78 ÷ 3.0625 = 25.5
- 4
Healthy weight range for this height
Range = 18.5 × Height² … 24.9 × Height²
18.5 × 3.0625 … 24.9 × 3.0625 = 56.7 – 76.3 kg
- Underweight
- Normal
- Overweight
- Obese I
- Obese II+
Good to know: BMI does not distinguish muscle from fat — read it together with waist size or body-fat percentage.
BMI Calculator — how it works
Formula
BMI = weight (kg) ÷ height² (m). Remember to convert height from centimetres to metres: 180 cm = 1.80 m, squared is 3.24. So 82 kg / 3.24 = 25.3.
WHO categories
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal (healthy) |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese (class 1) |
| 35.0 – 39.9 | Obese (class 2) |
| 40 and above | Severely obese (class 3) |
What BMI doesn't see
BMI can't tell muscle from fat. A muscular athlete may read "overweight," while someone with low muscle mass may look "normal" yet carry a high fat percentage. That's why BMI should be read alongside waist circumference and body fat percentage, not on its own — a waist-to-hip ratio calculator and a body fat calculator complete the picture. In children and pregnancy the adult BMI thresholds don't apply; percentile charts are used instead.
Finding your healthy weight range
Run the same formula in reverse: your height squared × 18.5 (lower bound) and × 24.9 (upper bound). For 1.80 m the healthy range is 59.9 – 80.7 kg. Where in that range you aim is personal; staying within it is what matters.
Worked example
Someone 1.80 m tall weighing 82 kg: BMI = 82 ÷ (1.80 × 1.80) = 82 ÷ 3.24 = 25.3. That value has just crossed the 25.0 threshold, so it sits right at the start of the "overweight" category. Since the healthy range for their height is 59.9 – 80.7 kg, they are 1.3 kg above the upper bound — dropping to 80 kg would move them into the normal range. Being that close to a boundary shows how a few kilos can change the category.
Healthy weight range by height (BMI 18.5 – 24.9)
| Height | Healthy weight range |
|---|---|
| 150 cm | 41.6 – 56 kg |
| 155 cm | 44.4 – 59.8 kg |
| 160 cm | 47.4 – 63.7 kg |
| 165 cm | 50.4 – 67.8 kg |
| 170 cm | 53.5 – 72 kg |
| 175 cm | 56.7 – 76.3 kg |
| 180 cm | 59.9 – 80.7 kg |
| 185 cm | 63.3 – 85.2 kg |
| 190 cm | 66.8 – 89.9 kg |
| 195 cm | 70.3 – 94.7 kg |
| 200 cm | 74 – 99.6 kg |
WHO adult classification; muscle mass, age and sex can shift the range.
Frequently asked questions
How is BMI calculated?+
Divide your weight (kg) by the square of your height in metres: for 82 kg and 1.80 m, 82 ÷ 3.24 = 25.3. The tool lets you enter height in centimetres and converts it for you.
What is a normal BMI range?+
The WHO considers 18.5 – 24.9 normal (healthy). 25 and above is overweight, 30 and above is obese; below 18.5 is underweight.
Why can BMI be misleading for athletes?+
BMI can't distinguish muscle from fat, and muscle is heavy, so very muscular people can read "overweight." In that case waist circumference and body fat percentage are better indicators.
What is my ideal weight for my height?+
The healthy range is your height squared × 18.5 to × 24.9 (59.9 – 80.7 kg for 1.80 m). For a single "ideal" figure using the Devine formula, use an ideal weight calculator.
Can I use this to calculate my child's BMI?+
No — adult thresholds don't apply to children; they need age- and sex-specific percentile assessment. For infants, use a baby weight or baby height reference.
Does BMI alone tell me if I'm healthy?+
No, it is a screening tool. Blood values, waist circumference, muscle-fat distribution and lifestyle all matter; for a definitive assessment consult your doctor.
Sources
Related guides
About this page
- Publisher:
- Kalkoro — Teknolojig Bilişim Teknolojileri A.Ş., İstanbul
- Written by:
- Kübra Yıldız — Editor (Health, nutrition, pregnancy, education, exam scores)
- Reviewed by:
- Furkan Tur — Editor
Parameters come from official sources; the last update date is shown at the bottom of the page.
Spotted a wrong result? Use the "Report a bug" button at the top of the page; every report is reviewed.
How we calculate and our accuracy policy →
This tool is for general information only and is not medical diagnosis, treatment or advice. Consult a physician for decisions about your health.
Last updated: