⚖️ BMI Calculator
Calculate your Body Mass Index instantly — free, no signup
| Category | BMI Range | Health Risk |
|---|---|---|
| Underweight | Below 18.5 | Malnutrition risk |
| Normal Weight | 18.5 – 24.9 | Low risk ✅ |
| Overweight | 25.0 – 29.9 | Moderate risk |
| Obese Class I | 30.0 – 34.9 | High risk |
| Obese Class II | 35.0 – 39.9 | Very high risk |
| Obese Class III | 40.0 and above | Extremely high risk |
Free BMI Calculator
Check Your Body Mass Index Instantly
Calculate BMI in seconds — metric or imperial, with healthy weight range & personalized tips.
What Is BMI and Why Does It Matter?
BMI — Body Mass Index — is one of the most widely used health screening tools in the world. It's a simple calculation based on your height and weight that gives you an indication of whether your body weight is in a healthy range. Doctors, health professionals, and fitness experts across Europe, the US, and worldwide use BMI as a quick first step in assessing weight-related health risks.
While BMI is not a perfect measure of health (more on that below), it is a useful, free, and instant way to check if your weight may be putting you at risk for conditions like heart disease, type 2 diabetes, high blood pressure, and certain cancers.
How Is BMI Calculated?
The BMI formula is straightforward:
For imperial units: BMI = (Weight in lbs × 703) ÷ Height (inches)²
Example: A person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9 — which is in the Normal range.
Our free BMI calculator does this math instantly — just enter your height and weight and click Calculate. It works in both metric (kg/cm) and imperial (lbs/ft/in) units.
BMI Categories – WHO Standard
The World Health Organization (WHO) defines the following BMI categories, which are used worldwide by doctors and health systems:
Underweight
May indicate malnutrition or an underlying health condition
Normal Weight
Healthy range — associated with lowest health risks
Overweight
Moderate health risk — lifestyle changes recommended
Obese
High health risk — medical advice strongly recommended
| BMI Range | Category | Health Risk | Action Recommended |
|---|---|---|---|
| Below 18.5 | Underweight | Malnutrition, osteoporosis, low immunity | See a doctor, increase calorie intake |
| 18.5 – 24.9 | Normal Weight ✅ | Lowest risk | Maintain healthy lifestyle |
| 25.0 – 29.9 | Overweight | Moderate — diabetes, heart disease risk | Diet & exercise changes |
| 30.0 – 34.9 | Obese Class I | High risk | Medical consultation recommended |
| 35.0 – 39.9 | Obese Class II | Very high risk | Medical treatment required |
| 40.0+ | Obese Class III | Extremely high risk | Urgent medical attention |
How to Use the BMI Calculator – Step by Step
Choose Your Unit System
Select Metric (kg/cm) if you use the standard system, or Imperial (lb/ft/in) if you're in the US or UK.
Enter Your Gender and Age
Select Male or Female and use the +/- buttons to set your age. These help provide more accurate health context.
Enter Your Height
Type your height or use the slider. For imperial, enter feet and inches separately.
Enter Your Weight
Type your weight in kg or lbs, or drag the slider to your weight.
Click Calculate BMI
Get your BMI score, category, color-coded gauge, healthy weight range, and personalized tips instantly.
Limitations of BMI – What It Doesn't Tell You
BMI is a useful starting point, but it has well-known limitations that are important to understand:
Muscle vs Fat
Muscular athletes often have a high BMI but very low body fat. BMI can't distinguish between muscle and fat weight.
Age Factor
Older adults tend to have more body fat at the same BMI as younger adults. BMI doesn't account for age-related changes.
Ethnicity
Research shows that South Asian, East Asian, and some other ethnic groups face higher health risks at lower BMI values.
Gender Differences
Women naturally carry more body fat than men at the same BMI. The standard BMI chart doesn't fully reflect this difference.
Fat Distribution
Where fat is stored matters. Belly fat (central obesity) is more dangerous than fat stored in the hips and thighs.
Not for Children
For children and teens, BMI is calculated differently using age- and gender-specific percentile charts.
How to Reach and Maintain a Healthy BMI
If You Are Underweight (BMI below 18.5)
- Increase calorie intake with nutritious foods — nuts, avocados, whole grains, dairy
- Eat 5–6 smaller meals throughout the day instead of 3 large ones
- Add protein to every meal — eggs, chicken, legumes, dairy
- Do strength training to build muscle mass
- Rule out underlying conditions with a doctor if you struggle to gain weight
If You Are Overweight or Obese (BMI 25 and above)
- Create a calorie deficit — reduce intake by 500 calories/day for ~0.5 kg weight loss per week
- Walk 30 minutes daily — one of the most effective and sustainable exercises
- Cut ultra-processed foods — biscuits, crisps, takeaways, sugary drinks
- Eat more protein and fibre — keeps you fuller for longer
- Sleep 7–8 hours — poor sleep increases hunger hormones (ghrelin)
- Track what you eat — most people underestimate calorie intake by 40%
BMI Standards Across Europe and the World
While the WHO BMI categories are used globally, some countries and health organizations have adopted slightly different cut-off points:
| Region / Standard | Overweight Starts At | Obese Starts At | Notes |
|---|---|---|---|
| 🌍 WHO (Global) | BMI 25.0 | BMI 30.0 | Used by most countries |
| 🇬🇧 UK (NHS) | BMI 25.0 | BMI 30.0 | Same as WHO standard |
| 🇩🇪 🇫🇷 EU (General) | BMI 25.0 | BMI 30.0 | WHO standard adopted |
| 🇮🇳 India / South Asia | BMI 23.0 | BMI 25.0 | Lower threshold due to higher risk at lower BMI |
| 🇨🇳 🇯🇵 East Asia | BMI 23.0 | BMI 27.5 | Asian-specific guidelines |
| 🇺🇸 USA (CDC) | BMI 25.0 | BMI 30.0 | Same as WHO standard |
