What is a normal BMI?

A normal or healthy BMI is between 18.5 and 24.9 according to WHO standards. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is considered obese.

What is the BMI formula?

BMI = Weight (kg) ÷ Height² (m²). In imperial units: BMI = (Weight in lbs × 703) ÷ Height² (inches²).

Is BMI accurate for everyone?

BMI is a general screening tool. It may not be accurate for athletes (high muscle mass), elderly people, pregnant women, or children. Consult a doctor for a full health assessment.

What BMI is considered obese?

A BMI of 30 or above is classified as obese by WHO. Class I obesity is 30–34.9, Class II is 35–39.9, and Class III (severe/morbid obesity) is 40 and above.

How do I calculate BMI in kg and cm?

BMI = Weight(kg) ÷ (Height(m))². Example: If you weigh 70kg and are 175cm tall: BMI = 70 ÷ (1.75)² = 70 ÷ 3.0625 = 22.9.

What is the ideal weight for my height?

Ideal weight is calculated as the weight range that gives a BMI between 18.5 and 24.9 for your height. Our calculator shows your exact ideal weight range instantly.

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BMI Calculator ⚖️

Calculate your Body Mass Index instantly. WHO-standard categories, ideal weight range, and personalized health insights. Works in both Metric and Imperial units.

Height centimeters (cm)

Weight kilograms (kg)

Age (optional) years

Gender (optional) for personalized tips

Your Body Mass Index

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1018.525303540+

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Ideal Min Weight

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Ideal Max Weight

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Weight to Goal

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BMI Prime

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Ponderal Index

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WHO Category

💡 Health Insights

⚠️ Medical Disclaimer: BMI is a general screening tool and is not a diagnostic measure. It may not accurately reflect body composition for athletes, elderly, pregnant women, or children. Always consult a qualified healthcare professional for personalized medical advice.

WHO BMI Classification Chart

The World Health Organization (WHO) defines these standard BMI categories for adults aged 18 and above.

Category	BMI Range	Health Risk	Action
Severe Underweight	< 16.0	Very High	Seek medical advice immediately
Underweight	16.0 – 18.4	High	Increase caloric intake, consult doctor
Normal Weight	18.5 – 24.9	Low (Healthy)	Maintain with balanced diet & exercise
Overweight	25.0 – 29.9	Increased	Exercise regularly, watch diet
Obese Class I	30.0 – 34.9	High	Consult doctor, lifestyle changes
Obese Class II	35.0 – 39.9	Very High	Medical intervention recommended
Obese Class III	≥ 40.0	Extremely High	Urgent medical attention required

Related Tools

How to Use the BMI Calculator

Choose Your Unit System

Select Metric (kg / cm) for most countries or Imperial (lbs / ft) for US measurements.

Enter Your Height

Type your height in centimeters (e.g. 170) or feet and inches (e.g. 5 ft 7 in).

Enter Your Weight

Enter your current body weight in kilograms or pounds. Use your actual weight for accuracy.

Add Age & Gender (Optional)

Optional fields for personalized health tips and context-specific insights.

View Your Results

See your BMI score, WHO category, ideal weight range, BMI Prime, and personalized health tips.

About the BMI Calculator

TheAshNow BMI Calculator uses the WHO-standard BMI formula and calculates results entirely in your browser. No data is stored or uploaded.

BMI Formula (Metric)

BMI = Weight (kg) ÷ Height² (m²). For example: 70 kg ÷ (1.75 m)² = 70 ÷ 3.0625 = 22.9 — Normal weight.

BMI Formula (Imperial)

BMI = (Weight in lbs × 703) ÷ Height² (inches²). For example: (154 lbs × 703) ÷ (67 in)² = 108,262 ÷ 4,489 = 24.1 — Normal weight.

What is BMI Prime?

BMI Prime is the ratio of your BMI to the upper limit of normal BMI (25). A BMI Prime of 1.0 or less means you are in or below the normal range. It makes it easier to compare across standards.

BMI Limitations

BMI does not distinguish between muscle and fat, so athletes or bodybuilders may show a high BMI despite being healthy. It is also less accurate for children, elderly people, and pregnant women. Use BMI as a starting point, not a final verdict.

Frequently Asked Questions

A normal or healthy BMI is between 18.5 and 24.9 according to the World Health Organization (WHO). Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.

Metric: BMI = Weight(kg) ÷ Height²(m²). Imperial: BMI = (Weight(lbs) × 703) ÷ Height²(inches²). Our calculator handles both automatically — just enter your numbers.

BMI is a general screening tool. It may overestimate fat in athletes (high muscle mass) and underestimate it in elderly or sedentary people. It is not recommended as the sole diagnostic tool. Always consult a healthcare professional.

A BMI ≥ 30 is classified as obese by WHO. This is further divided into Class I (30–34.9), Class II (35–39.9), and Class III or severe/morbid obesity (≥ 40). Each class carries progressively higher health risks.

Your ideal weight range is the weight that gives you a BMI between 18.5 and 24.9 for your height. Our BMI calculator automatically shows your minimum and maximum ideal weight after you enter your details.

Yes, 100% free and private. All calculations happen in your browser — no data is sent to any server, stored, or shared. No signup or registration required.