BMI Calculator
Calculate your Body Mass Index (BMI) to assess if your weight is healthy for your height.
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Great! Your weight is within the healthy range.
BMI Categories
| Category | BMI |
|---|---|
Severely Underweight | < 16 |
Underweight | 16 - 18.5 |
Normal Weight← You | 18.5 - 25 |
Overweight | 25 - 30 |
Obese (Class 1) | 30 - 35 |
Obese (Class 2) | 35 - 40 |
Obese (Class 3) | ≥ 40 |
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What is BMI?
BMI (Body Mass Index) is a simple measurement that uses your height and weight to estimate if your weight is healthy. It was invented in the 1830s by Belgian mathematician Adolphe Quetelet.
Think of BMI as a quick health screening tool—not a perfect diagnosis, but a useful starting point to understand where you stand.
BMI is used worldwide by doctors, fitness professionals, and health organizations because it's:
- Easy to calculate – Just need height and weight
- Inexpensive – No special equipment needed
- Standardized – Same categories used globally
BMI is a screening tool, not a diagnostic test. It doesn't measure body fat directly or account for muscle mass, bone density, or fat distribution.
The BMI Formula
The BMI formula is simple:
For imperial units (pounds and inches):
Example: A person who weighs 70 kg and is 1.75 m tall:
- BMI = 70 ÷ (1.75 × 1.75)
- BMI = 70 ÷ 3.0625
- BMI = 22.9
This falls in the "Normal Weight" category.
BMI Categories
The World Health Organization (WHO) defines these BMI categories for adults:
| Category | BMI Range |
|---|---|
| Severely Underweight | < 16 |
| Underweight | 16 - 18.5 |
| Normal Weight | 18.5 - 25 |
| Overweight | 25 - 30 |
| Obese (Class 1) | 30 - 35 |
| Obese (Class 2) | 35 - 40 |
| Obese (Class 3) | ≥ 40 |
The "Normal Weight" range (18.5-25) is associated with the lowest health risks for most people.
Limitations of BMI
BMI has several important limitations you should know:
-
Doesn't distinguish muscle from fat – Athletes with high muscle mass may have a "overweight" BMI despite being very fit.
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Doesn't show fat distribution – Where you carry fat matters. Belly fat (visceral fat) is more dangerous than fat on hips or thighs.
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Age differences – Older adults may have more body fat at the same BMI as younger adults.
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Ethnic variations – Health risks may differ at the same BMI for different ethnic groups. For example, Asians may have higher health risks at lower BMI values.
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Doesn't apply to everyone – BMI is designed for adults (18+). Children and teens use different growth charts.
For a complete health picture, combine BMI with waist circumference, body fat percentage, and other health markers like blood pressure and cholesterol.
Tips for a Healthy Weight
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Focus on overall health, not just the number – A slightly higher BMI with good fitness may be healthier than a "normal" BMI with poor habits.
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Make sustainable changes – Crash diets don't work long-term. Aim for gradual, permanent lifestyle changes.
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Stay active – Regular physical activity is crucial. Aim for at least 150 minutes of moderate exercise per week.
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Eat balanced meals – Focus on whole foods: vegetables, fruits, lean proteins, and whole grains.
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Get enough sleep – Poor sleep is linked to weight gain. Aim for 7-9 hours per night.
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Manage stress – Chronic stress can lead to emotional eating and weight gain.
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Consult professionals – If you're concerned about your weight, talk to a doctor or registered dietitian for personalized advice.