BMI Calculator
Enter your height and weight to calculate BMI instantly.
Supports both Japan Obesity Society and WHO standards.
Your BMI
<18.5 Normal
18.5-25 Overweight
25-30 Obesity I
30-35 Obesity II+
>35
Category
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Ideal Weight (BMI 22)
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Normal Weight Range
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Japan Obesity Society
| BMI | Category |
|---|---|
| <18.5 | Underweight |
| 18.5–25 | Normal weight |
| 25–30 | Obese (Class I) |
| 30–35 | Obese (Class II) |
| 35–40 | Obese (Class III) |
| ≥40 | Obese (Class IV) |
WHO Standard
| BMI | Category |
|---|---|
| <18.5 | Underweight |
| 18.5–25 | Normal weight |
| 25–30 | Overweight |
| 30–35 | Obesity Class I |
| 35–40 | Obesity Class II |
| ≥40 | Obesity Class III |
⚠️ This tool provides BMI as reference information only and is not a substitute for medical diagnosis. Consult a healthcare professional for health concerns.
What is a BMI Calculator?
A free online tool that instantly calculates your BMI (Body Mass Index) from your height and weight. It assesses obesity levels using both the Japan Obesity Society standards and WHO (World Health Organization) standards, and automatically calculates your ideal weight and healthy weight range based on BMI 22.0.
All calculations happen in your browser — your height and weight data are never sent to a server.
How to Use
Enter Your Height
Type your height in centimeters or drag the slider to adjust.
Enter Your Weight
Type your weight in kilograms or drag the slider. BMI is calculated instantly in real time.
Review Results
See your BMI value, category, ideal weight, and gauge bar at a glance.
Glossary
- BMI (Body Mass Index)
- A measurement calculated as weight (kg) ÷ height (m)². Used worldwide as an indicator of obesity.
- Ideal Weight
- The weight corresponding to BMI 22.0, calculated as height (m)² × 22. Statistically associated with the lowest disease risk.
- Japan Obesity Society Standard
- Japan's BMI classification standard. Obesity is defined as BMI ≥ 25, classified into degrees I–IV.
- WHO Standard
- The World Health Organization's BMI classification. Obesity is defined as BMI ≥ 30, which is higher than Japan's threshold.
- Basal Metabolic Rate (BMR)
- The amount of energy consumed at rest. Estimated from height, weight, age, and sex.
- Body Fat Percentage
- The proportion of body weight that is fat. BMI cannot distinguish muscle from fat, so body fat percentage is recommended alongside.
- Metabolic Syndrome
- A condition combining visceral obesity with two or more of: hypertension, high blood sugar, or dyslipidemia.
- Normal Weight Range
- The weight range corresponding to BMI 18.5–25.0, associated with the lowest health risks.
FAQ
- Q.What is the BMI formula?
- BMI = weight (kg) ÷ height (m)². Example: 65 kg ÷ (1.70 m)² ≈ 22.49.
- Q.Is my height and weight data sent to a server?
- No. All calculations are performed in your browser using JavaScript. No personal data is transmitted.
- Q.Why do the Japan and WHO standards give different assessments?
- People of Japanese descent show increased risk of lifestyle diseases at lower BMI levels. Japan's standard classifies obesity at BMI ≥ 25, stricter than the WHO threshold of ≥ 30.
- Q.What is ideal weight?
- The weight corresponding to BMI 22.0, calculated as height (m)² × 22. This BMI is statistically associated with the lowest disease risk.
- Q.Can muscular people have a high BMI?
- Yes. BMI does not distinguish between muscle and fat, so athletes with high muscle mass may have elevated BMI. Using BMI alongside body fat percentage is recommended.
- Q.Is this tool suitable for children?
- This tool targets adults (15+). Pediatric BMI assessment requires age- and sex-specific percentile standards.
Use Cases
🏋️ Diet Planning
Check your current obesity level and ideal weight to plan a diet program.
🏥 Pre-checkup Review
Know your BMI before your annual health check.
📊 Goal Setting
Understand your ideal weight range and set concrete weight loss/gain targets.
👨👩👧 Family Health Tracking
Quickly check BMI for the whole family.