BMI Calculator – Check Your Body Mass Index (Free, 2026)
BMI Calculator
For adults aged 18 and over
Your BMI Result
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is a simple number that compares your weight with your height. Doctors, dietitians and public health organizations use it as a quick first check to see whether a person's weight is likely to be too low, healthy, or too high for their height. It costs nothing, takes ten seconds, and needs no special equipment, which is why it is still the most widely used weight screening tool in the world.
This free BMI calculator works in kilograms, pounds, centimetres, or feet and inches. Enter your details and you will see your BMI, your weight category, and the weight range that counts as healthy for your height. Below the calculator you will find the formula, worked examples, a height and weight chart, and answers to the questions people ask most often.
How to Use This BMI Calculator
- Choose your weight unit (kg or lb) and height unit (cm, or feet and inches).
- Type in your weight.
- Type in your height. If you use feet and inches, enter the feet in the first box and the inches in the second.
- Press Calculate BMI.
- Read your BMI, your category, and your healthy weight range. The coloured bar shows where you sit on the scale.
For the most reliable result, weigh yourself in the morning in light clothing and measure your height without shoes.
The BMI Formula (Metric and Imperial)
BMI is your weight divided by your height squared. In metric units:
In pounds and inches, a constant of 703 is added to convert the units:
Example 1 (metric): A person who weighs 70 kg and is 175 cm (1.75 m) tall has a BMI of 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9, which is in the normal weight range.
Example 2 (imperial): A person who weighs 154 lb and is 5 ft 9 in (69 inches) tall has a BMI of 703 × 154 ÷ (69 × 69) = 108,262 ÷ 4,761 = 22.7, also in the normal range.
BMI Categories for Adults
The World Health Organization (WHO) groups adult BMI values into these standard categories:
- Below 18.5 - Underweight: Your weight may be too low for your height.
- 18.5 to 24.9 - Normal weight: Generally linked with the lowest risk of weight-related health problems.
- 25 to 29.9 - Overweight: The risk of conditions such as high blood pressure and type 2 diabetes begins to rise.
- 30 and above - Obese: Linked with a higher risk of heart disease, type 2 diabetes, and joint problems. Obesity is further divided into class I (30 to 34.9), class II (35 to 39.9), and class III (40 and above).
Healthy Weight Chart by Height
This chart shows the weight range that matches a BMI of 18.5 to 24.9 for common adult heights.
| Height | Healthy weight (kg) | Healthy weight (lb) |
|---|---|---|
| 150 cm (4 ft 11 in) | 41.6 - 56.0 | 92 - 123 |
| 155 cm (5 ft 1 in) | 44.4 - 59.8 | 98 - 132 |
| 160 cm (5 ft 3 in) | 47.4 - 63.7 | 104 - 140 |
| 165 cm (5 ft 5 in) | 50.4 - 67.8 | 111 - 149 |
| 170 cm (5 ft 7 in) | 53.5 - 72.0 | 118 - 159 |
| 175 cm (5 ft 9 in) | 56.7 - 76.3 | 125 - 168 |
| 180 cm (5 ft 11 in) | 59.9 - 80.7 | 132 - 178 |
| 185 cm (6 ft 1 in) | 63.3 - 85.2 | 140 - 188 |
BMI for South Asian and Other Asian Adults
Research shows that people of South Asian and some other Asian backgrounds can develop type 2 diabetes and heart disease at a lower BMI than people of European background. Because of this, some Asian guidelines, such as the WHO Asia-Pacific classification, treat a BMI of 23 or more as overweight and 25 or more as obese, rather than the standard 25 and 30.
What Your BMI Result Means and What to Do Next
If you are underweight
A low BMI can come from not eating enough, but also from medical causes such as thyroid problems, digestive conditions, or stress. If your BMI is below 18.5, speak with a doctor first. Gradual weight gain from regular meals, protein-rich foods, and strength training is usually safer than sudden changes.
If your weight is normal
Keep doing what works: balanced meals, regular movement, enough sleep, and regular health checks. Our guide on how to maintain a healthy BMI has simple daily habits that help. A normal BMI does not guarantee good health, so keep an eye on your waist size, blood pressure, and energy levels too.
If you are overweight
Small, steady changes work better than crash diets. Aim for slow weight loss of about 0.25 to 0.5 kg (roughly half to one pound) per week through better food choices, more daily walking (see whether 10,000 steps a day really helps), and a modest calorie deficit. Our guide on how a calorie deficit works explains how to set a realistic target. For food ideas that fit South Asian home cooking, read our Desi diet and weight loss guide, and for daily routines see the top 5 most effective weight loss habits.
If you are in the obese range
A BMI of 30 or above is a good reason to book a check-up. A doctor can look at blood sugar, blood pressure, and cholesterol, and help you build a safe, personal plan. Even a loss of 5 to 10 percent of your body weight can improve blood pressure and blood sugar.
After checking your BMI, work out how much protein suits your goal with the Protein Intake Calculator.
Waist Size: A Useful Second Number
BMI cannot show where your body stores fat, and fat around the belly carries more health risk than fat on the hips or thighs. To measure your waist, wrap a tape measure around the midpoint between your lowest rib and the top of your hip bone, after breathing out normally. For South Asian adults, a waist of 90 cm or more for men and 80 cm or more for women is commonly used as a warning level. For a deeper look at body composition, try our Body Fat Percentage Calculator.
Limits of BMI
- It cannot separate muscle from fat. Athletes and very muscular people can have a high BMI with low body fat. Our comparison of BMI vs body fat percentage explains the difference.
- It ignores fat distribution. Two people with the same BMI can have very different amounts of belly fat.
- It can be less accurate for older adults, who lose muscle with age, so a normal BMI may hide low muscle and higher fat.
- It does not apply during pregnancy. Weight gain in pregnancy is guided by a doctor or midwife.
- It is not used the same way for children and teenagers, whose BMI is compared with age and sex growth charts.
Is BMI Different for Men and Women?
The formula and the standard categories are the same for men and women. However, at the same BMI, women usually carry a higher percentage of body fat than men, and body fat tends to increase with age. That is one more reason to use BMI as a screening tool and combine it with other measurements.
Frequently Asked Questions (FAQs)
Q1: What is a healthy BMI?
Answer: For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is classed as obese.
Q2: How do I calculate BMI in pounds and feet?
Answer: Convert your height to inches, square it, then divide your weight in pounds by that number and multiply the result by 703. This calculator does the conversion for you when you choose pounds and feet and inches.
Q3: Is BMI accurate for athletes?
Answer: Not always. Muscle weighs more than fat, so a muscular person can have a high BMI without excess body fat. For athletes, body fat percentage and waist size give a clearer picture.
Q4: Is BMI different for men and women?
Answer: No, the formula and categories are the same. But women usually have a higher body fat percentage than men at the same BMI.
Q5: Can children use this BMI calculator?
Answer: No. This calculator is for adults aged 18 and over. Children and teenagers are assessed with BMI-for-age percentile charts, so please ask a doctor or paediatrician.
Q6: Does a BMI of 23 mean overweight for South Asians?
Answer: Some Asian guidelines, including the WHO Asia-Pacific classification, use a lower cut-off and treat a BMI of 23 or more as overweight, because health risks can rise at lower BMI values. Ask your doctor which cut-offs apply to you.
Q7: How often should I check my BMI?
Answer: Every month or two is plenty. BMI changes slowly, and day-to-day weight swings from water and food are normal.
Q8: Is BMI enough to judge my health?
Answer: No. BMI is only a screening tool. For a fuller picture, look at your waist size, blood pressure, blood sugar, cholesterol, activity level, and sleep, and have regular check-ups with a doctor.
Related Guides and Tools
➡️ Understand the difference: BMI vs Body Fat Percentage
➡️ Build healthy habits: How to Maintain a Healthy BMI
➡️ Set a realistic weight loss target: Calorie Deficit Explained
➡️ Look beyond BMI: Body Fat Percentage Calculator
➡️ Eat well for your goal: Desi Diet and Weight Loss
➡️ Plan your meals: How Much Protein Do You Really Need?
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This calculator and article are for general information only and are not medical advice. Please speak with a doctor before making major changes to your diet or exercise routine.
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