💪 BMI Calculator

Calculate your Body Mass Index (BMI) to understand your current weight status and identify your healthy weight range. Provides WHO BMI classification along with BMI Prime, Ponderal Index, and other health indicators.

BMI standard

Age (years)

Gender

Male Female

Height (cm)

Weight (kg)

BMI (Body Mass Index)

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BMI Prime — Ponderal Index (PI) —

Healthy Weight Range

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To Healthy Weight

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GUIDE

Learn more

What is BMI?

BMI (Body Mass Index) is an obesity measurement indicator calculated from the ratio of height to weight. Developed by Belgian mathematician Adolphe Quetelet in 1832, it is the most widely used weight assessment tool worldwide.

BMI Calculation Formula

BMI = weight(kg) ÷ (height(m))²

Example: Weight 70kg, Height 175cm
BMI = 70 ÷ (1.75)² = 22.86

WHO BMI Classification

Category	BMI Range	Health Risk
Severe Thinness	< 16	High
Moderate Thinness	16 - 16.9	Moderate
Mild Thinness	17 - 18.4	Low
Normal	18.5 - 24.9	Minimal
Overweight	25 - 29.9	Low
Obese Class I	30 - 34.9	Moderate
Obese Class II	35 - 39.9	High
Obese Class III	≥ 40	Very High

Health Risks of Overweight/Obesity

Being overweight or obese increases the risk of the following health problems:
• Type 2 diabetes
• High blood pressure and cardiovascular disease
• Stroke
• Certain cancers (colon, breast, uterine, etc.)
• Osteoarthritis
• Sleep apnea
• Fatty liver disease

Health Risks of Being Underweight

Being underweight can also cause the following health problems:
• Malnutrition and weakened immune system
• Osteoporosis
• Anemia
• Reproductive dysfunction
• Growth and development delays (in adolescents)

Limitations of BMI

While BMI is a useful indicator, it has the following limitations:
• Does not distinguish between muscle mass and fat mass
• Athletes or muscular individuals may be classified as overweight
• Does not adequately account for differences in age, gender, and ethnicity
• Does not consider fat distribution such as abdominal obesity

Therefore, BMI should be used as one tool for health assessment, and it is recommended to evaluate it comprehensively with other indicators such as body fat percentage and waist circumference.

What is BMI Prime?

BMI Prime is your actual BMI divided by 25 (the overweight threshold). A value of 1.0 or higher indicates overweight, while below 1.0 indicates normal or underweight. For example, a BMI Prime of 1.2 means you are 20% heavier than normal weight.

What is Ponderal Index?

Ponderal Index (PI) is similar to BMI but uses the cube of height in its calculation. PI provides a more accurate indicator for tall and short individuals. The normal range is approximately 12-13.

When to See a Doctor

Professional consultation is recommended in the following cases:
• BMI is 30 or higher
• BMI is below 18.5
• Rapid weight changes in a short period
• Obesity-related health problems (diabetes, high blood pressure, etc.)
• Difficulty managing weight

Frequently asked questions

How exactly is BMI calculated?

BMI is weight in kilograms divided by height in meters squared. For example, 70kg at 175cm gives a BMI of 22.86.

Can BMI accurately assess athletes?

Not always - BMI cannot distinguish muscle from fat, so muscular athletes may be classified as overweight even when they are healthy. Checking body fat percentage alongside BMI gives a fuller picture.

Why does the calculator also show BMI Prime and Ponderal Index?

BMI Prime shows how your BMI compares relative to the overweight threshold (25), and Ponderal Index uses height cubed for a more accurate reading for very tall or short people - both complement the standard BMI figure.

Should I see a doctor if my BMI is outside the normal range?

Consultation is recommended if your BMI is 30+ or below 18.5, or if you have had rapid recent weight change. Still, don't rely on BMI alone - consider it alongside other health indicators.

TRUST & SOURCES

Methodology and official sources

The formula, adult classification basis, scope, and limits are disclosed together.

Official status: This is a Util Monster reference calculator, not a medical diagnostic tool.
Effective date: 2025-12-08
Last reviewed: 2026-07-30

Method

BMI = weight (kg) ÷ height (m)². Adult results reference WHO thresholds of BMI 25 or more for overweight and BMI 30 or more for obesity.

Worked example

70 kg ÷ (1.75 m × 1.75 m) = BMI 22.86.

Limitations

Adult cut-offs do not apply directly to children or adolescents.
BMI does not distinguish muscle mass, fat distribution, pregnancy, or individual medical history.
Health decisions may require clinical assessment and additional measures.

Sources

Obesity and overweight World Health Organization · Official source
Malnutrition fact sheet World Health Organization · Official source