BMI Calculator

Calculate your Body Mass Index (BMI) and find out your healthy weight range.

Unit System Choose Metric (kilograms / centimeters) or Imperial (pounds / inches).

Weight Your body weight, entered in the unit system selected above.

Height Your height, entered in the unit system selected above.

Age Your age. BMI categories are the same for adults of all ages, but age gives context to your result.

Your BMI 22.86

Category Normal Weight

Healthy Weight Range 56.7–76.3 kg

Editorial Standard

GetCalcu Methodology & Editorial Standards

Reviewed: September 2026

Body Mass Index (BMI) is an anthropometric screening metric defined as body mass divided by the square of body height. It provides an initial population-level estimate of weight categories but is not an individualized medical diagnosis.

Key Modeling Assumptions:

Standard adult weight categories apply to individuals aged 20 years and older.
The calculation assumes uniform body density and does not distinguish between skeletal muscle mass, bone density, and adipose tissue.
Clinical assessments should incorporate complementary markers including waist circumference, body fat percentage, and metabolic health panels.

Reference Sources: World Health Organization (WHO) — Body Mass Index Classification Guidelines • Centers for Disease Control and Prevention (CDC) — Defining Adult BMI • National Heart, Lung, and Blood Institute (NIH) — Clinical Guidelines on Obesity Identification

How to Calculate Your BMI and Understand Weight Categories

Body Mass Index (BMI) is a standardized screening metric used by healthcare providers and public health agencies globally to assess whether an individual falls within an expected weight range for their height. While it serves as a helpful, accessible baseline, understanding what the numbers indicate—and what limitations exist—is critical for interpreting your results responsibly.

Standard Adult BMI Classifications (WHO & CDC)

Underweight (BMI below 18.5): Indicates body weight is below the expected range for height. May be associated with nutritional deficits, reduced immune function, or underlying conditions.

Normal / Healthy Weight (BMI 18.5–24.9): The statistical range associated with the lowest incidence of weight-related cardiovascular and metabolic health conditions in adult populations.

Overweight (BMI 25.0–29.9): Indicates weight greater than the standard reference range. Healthcare providers generally evaluate lifestyle factors and waist measurements to assess individual risk.

Obesity Class I (BMI 30.0–34.9), Class II (BMI 35.0–39.9), and Class III (BMI 40.0+): Correlated with elevated risk of hypertension, type 2 diabetes, cardiovascular disease, and sleep apnea.

Important Clinical Limitations of BMI

Muscle vs. Fat Composition: Because muscle tissue is denser than adipose fat tissue, athletes, weightlifters, and muscular individuals may register an "overweight" or "obese" BMI despite having low body fat and excellent cardiovascular fitness.

Age and Gender Differences: Women naturally carry higher essential body fat percentages than men at identical BMI levels. Similarly, older adults often experience sarcopenia (loss of muscle mass) while body fat increases, which may mask health risks at a "normal" BMI.

Ethnicity Considerations: Research endorsed by the WHO indicates that health risks associated with obesity may begin at lower BMI thresholds (such as 23.0 for overweight and 27.5 for obesity) in certain Asian populations.

How Healthy Weight Ranges Are Determined

Your healthy weight range is calculated by applying the normal BMI boundaries (18.5 to 24.9) to your specific height squared: Healthy Min = 18.5 × Height(m)², and Healthy Max = 24.9 × Height(m)². This gives a realistic span of healthy weights rather than a single rigid number.

How to Use the BMI Calculator

1
Choose your preferred unit system: Metric (kilograms and centimeters) or Imperial (pounds and inches).
2
Enter your current body weight and height.
3
Optionally specify your age to provide demographic context.
4
Review your calculated BMI value, color-coded classification, and customized healthy weight span on the visual gauge.
5
Consult a licensed healthcare professional before initiating significant dietary or fitness modifications.

Body Mass Index Formula

BMI = Weight (kg) / [Height (m)]² | Imperial: BMI = 703 × Weight (lb) / [Height (in)]²

BMI divides total body weight by height squared. For imperial measurements, a conversion factor of 703 is applied to reconcile pounds and inches to metric kilograms per square meter.

Variable Definitions:

BMI: Body Mass Index (kg/m²)
Weight (kg): Body mass in kilograms (or pounds converted via × 0.453592)
Height (m): Stature in meters (or inches converted via × 0.0254)
Healthy Min Weight: 18.5 × [Height in meters]²
Healthy Max Weight: 24.9 × [Height in meters]²

Real-World Worked Examples

These scenarios demonstrate how key input parameters alter your calculation outcome.

Metric Reference Scenario

Input: Weight: 70.0 kg, Height: 175.0 cm (1.75 m), Age: 30

Result: BMI: 22.9 (Normal Weight) | Healthy Weight Range: 56.7–76.3 kg

A 70 kg individual at 175 cm falls comfortably in the center of the normal BMI range.

Imperial Reference Scenario

Input: Weight: 180.0 lb, Height: 70.0 in (5 ft 10 in), Age: 35

Result: BMI: 25.8 (Overweight) | Healthy Weight Range: 128.9–173.5 lb

At 180 lb, this individual is slightly above the 24.9 BMI cutoff (173.5 lb), indicating a screening recommendation to evaluate lifestyle and waist circumference.

Underweight Screening Scenario

Input: Weight: 45.0 kg, Height: 162.0 cm (1.62 m), Age: 25

Result: BMI: 17.1 (Underweight) | Healthy Weight Range: 48.5–65.3 kg

A BMI of 17.1 is below the 18.5 threshold, suggesting the individual is under the expected healthy weight for 162 cm.

Comprehensive Health Indicators Beyond BMI

To build an accurate assessment of health, clinical professionals typically pair BMI with these complementary metrics:

Waist-to-Height Ratio (WHtR)

Keeping your waist circumference under half your height (ratio < 0.50) is strongly correlated with lower cardiovascular and metabolic risk regardless of total weight.

Measures central abdominal fat distribution.

Body Fat Percentage

Direct measurement via DEXA scans, bioelectrical impedance, or calipers separates lean muscle mass from fat tissue.

Typical healthy ranges: 14–24% for men, 21–31% for women.

Cardiorespiratory Fitness

Aerobic endurance, muscular strength, resting heart rate, and VO2 max often provide more predictive value for longevity than scale weight alone.

Physical activity provides health benefits across all BMI tiers.

Metabolic & Blood Lipid Panels

Fasting blood glucose, HbA1c, triglycerides, HDL/LDL cholesterol, and blood pressure determine metabolic health status.

Essential clinical data from annual medical checkups.

Frequently Asked Questions

How is Body Mass Index (BMI) calculated?

BMI is calculated by dividing body weight in kilograms by height in meters squared (kg/m²). For imperial measurements, multiply weight in pounds by 703 and divide by height in inches squared: BMI = (Weight in lb × 703) ÷ (Height in inches)². Our calculator automates these conversions seamlessly.

What are the official adult BMI categories?

According to the World Health Organization (WHO) and CDC, adult BMI is classified as: Underweight (below 18.5), Normal Weight (18.5 to 24.9), Overweight (25.0 to 29.9), and Obese (30.0 or higher).

Why can BMI be misleading for athletes and bodybuilders?

BMI does not differentiate between skeletal muscle and body fat. Because muscle is approximately 18% denser than fat by volume, highly trained athletes with substantial muscle mass and low body fat frequently register in the "overweight" or "obese" BMI categories.

How is the healthy weight range determined for my height?

The healthy weight range corresponds to the minimum (18.5) and maximum (24.9) normal BMI thresholds applied to your height. For example, for someone 175 cm tall, the range is 18.5 × (1.75)² = 56.7 kg to 24.9 × (1.75)² = 76.3 kg.

Do BMI categories differ for men and women?

Standard clinical BMI classification tables are identical for adult men and women. However, women naturally maintain higher essential body fat levels than men with the same BMI, which is why body composition metrics provide helpful context.

Is BMI used the same way for children and teenagers?

No. For children and adolescents aged 2 to 19, BMI is calculated the same way but interpreted using age-and-sex-specific growth percentiles (CDC Growth Charts) rather than fixed adult category cutoffs.

What should I do if my BMI is in the overweight or underweight category?

Use your BMI as an informative initial screening point rather than a definitive diagnosis. Schedule an evaluation with a primary healthcare provider who can evaluate your blood pressure, metabolic markers, lifestyle, and body composition.