BMI Calculator
Calculate Body Mass Index (BMI) from height and weight. Get your BMI value, adult BMI category, and estimated healthy weight range with the LabProSuite BMI Calculator.
BMI is a screening measure based on height and weight. It does not directly measure body fat or distinguish fat mass from muscle mass. Interpret the result together with the individual's overall clinical and anthropometric profile.
BMI Result
Learn More About BMI
Read the complete LabProSuite guide covering the BMI formula, normal range, adult BMI categories, healthy weight calculation, clinical significance, and limitations.
Read the Complete BMI Guide →What Is BMI?
Body Mass Index (BMI) is a weight-for-height index commonly used to assess weight status in adults. It is calculated from body weight and height and is expressed in kilograms per square metre (kg/m²).
BMI is useful as a screening measure for underweight, normal weight, overweight, and obesity. However, it does not directly measure body fat or distinguish between muscle and fat mass. 1
BMI Formula
Adult BMI Categories
The standard adult BMI categories used by WHO are shown below. 2
| BMI (kg/m²) | Classification |
|---|---|
| <18.5 | Underweight |
| 18.5–24.9 | Normal weight |
| 25.0–29.9 | Overweight / Pre-obesity |
| 30.0–34.9 | Obesity Class I |
| 35.0–39.9 | Obesity Class II |
| ≥40.0 | Obesity Class III |
How Is BMI Calculated?
To calculate BMI, convert height to metres, square the height, and divide body weight in kilograms by the squared height.
BMI = 22.9 kg/m²
What Is a Healthy BMI?
For adults, a BMI of 18.5–24.9 kg/m² is commonly classified as normal weight. WHO uses this range in its adult BMI classification. 3
The BMI category should not be interpreted as an exact measurement of an individual's ideal body composition or overall health.
Healthy Weight Range Based on BMI
For a given adult height, the approximate weight corresponding to a BMI of 18.5–24.9 can be calculated using:
Therefore:
- Lower reference weight = 18.5 × height²
- Upper reference weight = 24.9 × height²
The healthy-weight range displayed by this calculator is mathematically derived from the standard adult BMI range. It is not an individualized medical target.
BMI Example
An adult weighing 80 kg with a height of 1.70 m has:
BMI ≈ 27.7 kg/m²
A BMI of approximately 27.7 kg/m² falls within the adult overweight range under the standard classification.
Why BMI Is Clinically Useful
Higher BMI is associated with increased risk of several chronic conditions, including cardiovascular disease, diabetes, hypertension, and certain cancers. WHO describes BMI as a useful indicator of nutritional status and disease risk at the population and individual screening level. 4
Limitations of BMI
- BMI does not directly measure body fat percentage.
- BMI cannot distinguish muscle mass from fat mass.
- A muscular person may have a relatively high BMI despite having relatively low body fat.
- BMI does not indicate where body fat is distributed.
- Waist circumference can provide additional information about central adiposity.
- BMI interpretation can differ among populations and individuals.
WHO notes that BMI may not correspond to the same degree of body fatness in different populations and that additional measurements may be useful when assessing adiposity. 5
BMI for Children and Adolescents
Adult BMI categories should not simply be applied to children and adolescents. For younger people, BMI is interpreted according to age and sex using appropriate growth references or BMI-for-age measures. 6
This calculator is designed primarily for adult BMI calculation. Children and adolescents require age- and sex-specific interpretation.
BMI During Pregnancy
Standard adult BMI categories are not intended to assess pregnancy weight changes. Pregnancy weight should be evaluated using appropriate prenatal guidance and clinical assessment.
How to Use the LabProSuite BMI Calculator
- Enter your weight.
- Select kg or lb.
- Choose your height input method.
- Enter height in cm, metres, or feet and inches.
- Click Calculate BMI.
- Review your BMI and adult BMI category.
- Review the mathematically derived reference healthy-weight range.
Complete BMI Reference Guide
For a detailed explanation of BMI formula, categories, healthy weight range, limitations, and interpretation:
BMI Calculator: Formula, Normal Range & Interpretation →Frequently Asked Questions
What is BMI?
BMI stands for Body Mass Index. It is calculated by dividing weight in kilograms by height in metres squared.
What is a normal BMI?
For adults, BMI from 18.5 to 24.9 kg/m² is commonly classified as normal weight.
What BMI is considered overweight?
For adults, BMI from 25.0 to 29.9 kg/m² is commonly classified as overweight or pre-obesity.
What BMI is considered obesity?
For adults, BMI of 30 kg/m² or higher is classified as obesity.
Is BMI the same as body fat percentage?
No. BMI is calculated from height and weight and does not directly measure body fat percentage.
Can muscular people have a high BMI?
Yes. BMI does not distinguish muscle mass from fat mass, so muscular individuals can have a higher BMI without having excessive body fat.
Is BMI different for children?
Yes. Children and adolescents require age- and sex-specific BMI interpretation rather than standard adult BMI categories.
What is the BMI formula?
BMI = Weight in kilograms divided by height in metres squared.
Disclaimer
This calculator is provided for educational and laboratory reference purposes only. BMI is a screening measure and should not be used as the sole basis for diagnosis, treatment, or medical decision-making.
Clinical interpretation should consider the individual's complete clinical history, body composition, waist circumference, laboratory findings, and applicable clinical guidance.
References
- World Health Organization (WHO) — Nutrition for a healthy life.
- World Health Organization (WHO) — Obesity and overweight.
- WHO Nutrition Landscape Information System — Adult BMI classification.
