BMI Calculator

Calculate your BMI from height and weight in metric or imperial units, with your category and healthy weight range.

Weight (kg)

Height (cm)

Enter your weight and height.

About This Tool

NinjaFunction's BMI Calculator works out your Body Mass Index from your weight and height. Use kilograms and centimetres, or pounds, feet and inches. It shows your BMI, the WHO adult category and the healthy weight range for your height. BMI is a screening guide, not a medical diagnosis. Your numbers stay in your browser.

🔑 How to Use

Choose metric or imperial units.
Enter your weight and height.
Read your BMI and the category.
See the healthy weight range for your height.

💡 Pro Tips

✔ Measure without shoes and weigh in the morning for steadier numbers.
✔ Imperial: enter feet and inches in the two height boxes.
✔ This is not medical advice. Speak to a doctor about your health.

BMI Categories (Adults)

BMI	Category
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25 – 29.9	Overweight
30 and above	Obese

BMI Ranges and What They Mean

BMI	WHO adult category	Note
Below 18.5	Underweight	May point to low nutrition or an underlying issue
18.5 – 24.9	Normal weight	Lowest average health risk
25 – 29.9	Overweight	Risk rises, especially with a large waist
30 and above	Obese	Higher risk of heart disease and diabetes

What BMI Cannot Tell You

Muscle vs fat. A fit athlete with a lot of muscle can have a high BMI and low body fat.
Where fat is stored. Fat around the waist is riskier than fat on the hips. Waist size is a useful second check.
Age and sex. Older adults and women tend to carry more fat at the same BMI.
Children and teenagers. They use age-based growth charts, not this scale.
Pregnancy. BMI does not apply.

Healthy Weight Range

The tool also shows the weights that give a BMI between 18.5 and 24.9 for your height. For a person who is 175 cm tall, that is about 56.7 to 76.3 kg. The range is wide because bodies differ, so being near either end is not a problem by itself.

Next Steps

BMI is a first check, not a diagnosis. If your result is outside the normal range, or you are worried about your weight, speak to a doctor or a registered dietitian. They can look at your waist size, blood tests, fitness, family history and diet, which a single number cannot show.

Frequently Asked Questions

How is BMI calculated?

BMI = weight in kilograms ÷ (height in metres)². A person who weighs 70 kg and is 1.75 m tall has a BMI of 22.9.

What is a healthy BMI?

For adults, the WHO ranges are: under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, and 30 or more obese.

Is BMI accurate for everyone?

No. It does not separate muscle from fat, so athletes can score high. It also does not suit children, older adults or pregnant women. Use it as a guide only.

Do Asian adults use a different scale?

Some health bodies suggest lower cut-offs for South Asian adults, for example overweight from 23. Ask your doctor which applies to you.

Is my data stored?

No. The numbers stay in your browser.

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