What is a healthy BMI?

A healthy BMI for adults is between 18.5 and 24.9. This range is associated with the lowest risk of weight-related health problems. However, BMI does not account for muscle mass, bone density, or body composition.

How is BMI calculated?

BMI is calculated by dividing your weight in kilograms by your height in meters squared. The formula is: BMI = weight (kg) / height (m)². For imperial units: BMI = 703 × weight (lbs) / height (in)².

What is the BMI formula?

The metric BMI formula is: BMI = weight (kg) ÷ [height (m)]². The imperial formula is: BMI = 703 × weight (lbs) ÷ [height (in)]². Both formulas produce the same result.

BMI is a useful screening tool for the general population but has limitations. It does not distinguish between muscle and fat mass, so athletes or muscular individuals may have a high BMI despite being healthy. It also doesn't account for age, sex, ethnicity, or body fat distribution.

What BMI is considered obese?

A BMI of 30 or higher is considered obese. Obesity is further classified into Class I (BMI 30–34.9), Class II (BMI 35–39.9), and Class III or severe obesity (BMI 40+).

What is a normal BMI for a woman / man?

The healthy BMI range of 18.5–24.9 applies to both men and women. However, women tend to have more body fat than men at the same BMI. For a more accurate assessment, consider consulting a healthcare professional who can evaluate body composition directly.

BMI Calculator

Calculate your Body Mass Index using metric or imperial units. Instantly see your BMI category and healthy weight range.

📏 Metric BMI Calculator

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Enter your weight and height above to calculate your BMI

Metric formula: BMI = weight (kg) ÷ height (m)² | Imperial formula: BMI = 703 × weight (lbs) ÷ height (in)²

Quick Reference — BMI at 170 cm

Weight	BMI	Category
60 kg (132 lbs)	20.8	Normal
70 kg (154 lbs)	24.2	Normal
80 kg (176 lbs)	27.7	Overweight
90 kg (198 lbs)	31.1	Obese

What Is BMI?

Body Mass Index (BMI) is a simple numerical value derived from your weight and height. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and is widely used as a quick screening tool to categorize individuals into weight categories: underweight, normal weight, overweight, and obese.

BMI does not directly measure body fat, but research has shown it correlates reasonably well with more direct measures of body fat for most people. It is used by healthcare professionals as an initial assessment tool to identify potential weight-related health risks.

The BMI Formula

The metric formula is: BMI = weight (kg) ÷ [height (m)]². For example, a person weighing 70 kg who is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9.

The imperial formula is: BMI = 703 × weight (lbs) ÷ [height (in)]². For example, a person weighing 154 lbs who is 68 inches tall has a BMI of 703 × 154 ÷ (68 × 68) = 108,262 ÷ 4,624 = 23.4.

Limitations of BMI

While BMI is a useful population-level screening tool, it has several well-known limitations:

Muscle mass: Athletes and muscular individuals may have a high BMI despite having low body fat. A bodybuilder with significant muscle mass could be classified as "overweight" or "obese" by BMI alone.
Age: Older adults tend to have more body fat than younger adults at the same BMI. BMI may underestimate body fat in elderly individuals.
Sex: Women typically have more body fat than men at the same BMI level.
Ethnicity: BMI cutoffs may not be equally applicable across all ethnic groups. For example, Asian populations may have higher health risks at lower BMI values.

Healthy BMI Ranges for Adults

The World Health Organization (WHO) defines the following BMI categories for adults aged 20 and older:

Underweight: BMI below 18.5 — may indicate nutritional deficiency or other health issues.
Normal weight: BMI 18.5 to 24.9 — associated with the lowest health risks.
Overweight: BMI 25 to 29.9 — increased risk of cardiovascular disease and type 2 diabetes.
Obese: BMI 30 and above — significantly increased risk of various health conditions.

Frequently Asked Questions

What is a healthy BMI?: A healthy BMI for adults is between 18.5 and 24.9. This range is associated with the lowest risk of weight-related health problems. However, BMI is just one factor — body composition, waist circumference, and overall fitness matter too.
How is BMI calculated?: BMI is calculated by dividing your weight in kilograms by your height in meters squared: BMI = kg / m². For imperial units, multiply weight in pounds by 703, then divide by height in inches squared.
What is the BMI formula?: Metric: BMI = weight (kg) ÷ [height (m)]². Imperial: BMI = 703 × weight (lbs) ÷ [height (in)]². Both formulas yield the same BMI value.
Is BMI accurate?: BMI is a useful screening tool for most people but has limitations. It doesn't distinguish between muscle and fat, so athletes may show a falsely high BMI. It also doesn't account for age, sex, or ethnicity differences in body composition.
What BMI is considered obese?: A BMI of 30 or higher is classified as obese. This is further divided into Class I (30–34.9), Class II (35–39.9), and Class III or severe obesity (40+).
What is a normal BMI for a woman / man?: The healthy BMI range of 18.5–24.9 applies to both men and women. However, women naturally have more body fat than men at the same BMI. For personalized advice, consult a healthcare professional.