How to use
Fill in Height (cm) and Weight (kg), and Result shows your BMI along with where it falls in the Japan Society for the Study of Obesity (JASSO) classification. The calculator accepts heights from 50 to 250 cm and weights from 2 to 400 kg.
- Category name: next to the English name you also see the official Japanese one, such as 普通体重 or 肥満（1度）. That makes it easy to match your result against a Japanese health check-up report or other Japanese material.
- Category bar: six equal-width segments, one per category, and a vertical line showing where your BMI lands. The top row of numbers (18.5, 25, 30, 35, 40) marks the BMI at which one category gives way to the next, and the bottom row is the weight in kg that produces each of those BMIs at your height. The category is picked from your BMI rounded to one decimal place, so you can land in the higher category while weighing about 0.1 kg less than the number below the bar.
- Notes: three lines covering the waist circumference used to diagnose metabolic syndrome, the ages BMI is used for, and a caution about reading an obesity result.
How JASSO classifies obesity
JASSO defines obesity as excess fat stored in adipose tissue together with a BMI of 25 or more, and divides it into four grades (1 to 4). Everything from 18.5 to under 25 is normal weight, and obesity grade 1 begins right at 25.
| Category (name on screen) | Japanese name | BMI | Weight where the category starts at 170 cm |
|---|---|---|---|
| Underweight | 低体重 | under 18.5 | |
| Normal weight | 普通体重 | 18.5 to under 25 | 53.5 kg |
| Obesity grade 1 | 肥満（1度） | 25 to under 30 | 72.3 kg |
| Obesity grade 2 | 肥満（2度） | 30 to under 35 | 86.7 kg |
| Obesity grade 3 | 肥満（3度） | 35 to under 40 | 101.2 kg |
| Obesity grade 4 | 肥満（4度） | 40 and above | 115.6 kg |
The last column is what you see under the bar when you enter a height of 170. At that height, a weight of 75 kg gives a BMI of 26.0, Obesity grade 1.
The classification table comes with two footnotes. One says that not every case of obesity at a BMI of 25 or more is a condition that medically requires weight loss. The other defines a BMI of 35 or more as severe obesity, which on screen means Obesity grade 3 and grade 4. The classification is also used for adults only.
Waist circumference and metabolic syndrome
The waist circumference in the first line of Notes is the one Japan uses to diagnose metabolic syndrome: 85 cm or more for men and 90 cm or more for women. The threshold for women is the higher of the two. You are considered to have metabolic syndrome if your waist meets that threshold and at least two of these three apply:
- Blood lipids: triglycerides of 150 mg/dL or more, or HDL cholesterol under 40 mg/dL
- Blood pressure: systolic of 130 mmHg or more, or diastolic of 85 mmHg or more
- Blood sugar: fasting blood glucose of 110 mg/dL or more
This calculator does not take a waist measurement or lab values. The BMI category reflects height and weight and nothing else, so measure your waist with a tape and compare it with the threshold separately.