BMI Calculator: Check Your Body Mass Index in Seconds
Want to know if your weight is right for your height? This free BMI calculator gives you your Body Mass Index in seconds. Use metric (kg/cm) or imperial (lbs/ft). No signup is needed.
What Is BMI?
BMI stands for Body Mass Index. It is a number that compares your weight to your height.
Doctors and health organizations use it as a quick screening tool. It helps show whether your weight may be too low, healthy, or too high for your height.
BMI does not measure body fat directly. It is a starting point, not a final diagnosis.
How to Use This BMI Calculator
It takes less than 30 seconds.
- Choose your unit: Metric (kg / cm) or Imperial (lbs / ft).
- Enter your height.
- Enter your weight.
- Click Calculate BMI.
- Click Reset to start again.
Your result will show your BMI number and the category it falls in.
BMI Formula
Metric Formula
BMI = weight (kg) ÷ height (m) × height (m)
Height must be in meters. To convert centimeters to meters, divide by 100.
Imperial Formula
BMI = 703 × weight (lbs) ÷ height (inches) squared
To convert feet to inches, multiply the feet by 12 and add the extra inches.
BMI Calculation Examples
Example 1: Metric
- Height: 170 cm (1.70 m)
- Weight: 68 kg
BMI = 68 ÷ (1.70 × 1.70) = 68 ÷ 2.89 = 23.5
This falls in the normal weight range.
Example 2: Imperial
- Height: 5 ft 6 in (66 inches)
- Weight: 150 lbs
BMI = 703 × 150 ÷ (66 × 66) = 105,450 ÷ 4,356 = 24.2
This also falls in the normal weight range.
BMI Categories for Adults
These ranges are from the World Health Organization (WHO). They apply to adults aged 20 and older.
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity (Class I) |
| 35.0 – 39.9 | Obesity (Class II) |
| 40.0 and above | Obesity (Class III) |
What Does Your BMI Result Mean?
Underweight (Below 18.5)
Your weight may be too low for your height. This can happen due to poor nutrition, illness, or other health conditions. If your BMI is in this range, talk to a doctor to find the cause.
Normal Weight (18.5 – 24.9)
Your weight is in the range linked with the lowest health risks for most people. Keep up balanced eating, regular activity, and good sleep.
Overweight (25.0 – 29.9)
Your weight is above the usual healthy range. Small, steady changes in food and activity can help. Your doctor can guide you if needed.
Obesity (30.0 and Above)
A higher BMI is linked with a greater risk of conditions like type 2 diabetes, high blood pressure, and heart disease. A healthcare professional can help you build a safe, personal plan.
BMI Ranges for Asian Adults
Health risks can begin at a lower BMI in people of South Asian and other Asian backgrounds. Because of this, many health bodies in Asia, including guidelines used in India, use lower cut-offs:
- Normal weight: 18.5 – 22.9
- Overweight: 23.0 – 24.9
- Obese: 25.0 and above
If you are of Asian origin, keep these ranges in mind when reading your result. Your doctor can tell you which range suits you best.
Healthy Weight Range for Your Height
You can work backward from the healthy BMI range of 18.5 to 24.9.
For example, at 170 cm, a healthy weight range is about 53.5 kg to 72 kg.
To find your own range:
- Lower limit = 18.5 × height (m) × height (m)
- Upper limit = 24.9 × height (m) × height (m)
Limits of BMI: What It Cannot Tell You
BMI is useful, but it has limits. Knowing them helps you read your result correctly.
- It does not measure body fat. It cannot tell fat from muscle.
- Athletes and muscular people may show a high BMI even with low body fat.
- Older adults may have a normal BMI but low muscle mass.
- It does not show where fat is stored. Fat around the belly carries more health risk than fat elsewhere.
- Pregnant women should not use BMI to check their weight.
- Children and teens need a different method (see below).
Is BMI Different for Children and Teens?
Yes. For people aged 2 to 19, BMI is compared with children of the same age and sex. The result is shown as a percentile, not a fixed category.
This calculator is made for adults. For a child or teen, please ask a pediatrician or use a growth chart made for children.
Other Measures to Use Along with BMI
For a fuller picture of your health, you can also check:
- Waist circumference: A large waist can signal higher health risk.
- Waist-to-hip ratio: Compares fat around your waist and hips.
- Body fat percentage: Shows how much of your weight is fat.
- Blood pressure, blood sugar, and cholesterol: Checked through simple medical tests.
Simple Tips to Reach or Keep a Healthy BMI
- Eat more vegetables, fruits, whole grains, and protein.
- Cut back on sugary drinks and heavily processed food.
- Aim for at least 150 minutes of moderate activity each week.
- Sleep 7 to 9 hours each night.
- Aim for slow, steady change rather than crash diets.
- Get regular health check-ups.
Frequently Asked Questions (FAQs)
What is a good BMI?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. For Asian adults, the healthy range is usually 18.5 to 22.9.
Is BMI accurate?
BMI is a good screening tool for large groups of people. For one person, it can be misleading because it ignores muscle, bone, and fat distribution. Use it as a guide, not a final answer.
Is BMI the same for men and women?
For adults, the BMI formula and categories are the same for men and women. However, women often have more body fat than men at the same BMI.
How often should I check my BMI?
Once a month is enough. Weight changes slowly, so checking too often can cause needless worry.
Can I have a high BMI and still be healthy?
Yes, it is possible, especially for very muscular people. But a high BMI in most people goes with higher health risks. A doctor can check your overall health.
Can I have a normal BMI and still be unhealthy?
Yes. Some people with a normal BMI carry extra fat around the belly or have low muscle. Diet, activity, and medical tests also matter.
How do I convert my height from feet to centimeters?
Multiply feet by 30.48 and inches by 2.54, then add the two. For example, 5 ft 6 in = (5 × 30.48) + (6 × 2.54) = 167.6 cm.
How do I convert pounds to kilograms?
Multiply pounds by 0.4536. For example, 150 lbs × 0.4536 = 68 kg.
Does BMI change with age?
The formula stays the same for adults. But body composition changes with age, so older adults should also check muscle strength and overall health.
Final Note
BMI is a quick and simple way to start understanding your weight. Use it as one piece of the puzzle, along with how you feel, how you eat, how active you are, and your medical check-ups.
If your result worries you, speak with a doctor or a registered dietitian.
Disclaimer: This calculator and page are for general information only. They are not medical advice. Always consult a qualified healthcare professional about your health.