BMI Calculator

BMI Calculator

Free Body Mass Index calculator with Imperial and Metric support. Get your BMI, weight category, color gauge, healthy weight range, BMI Prime, Ponderal Index, estimated body fat percentage, and waist-to-height ratio — all in one place. No login, no limits, works entirely in your browser.

Enter Your Measurements

Select a unit system, fill in your details, and press Calculate

Unit System:

Gender (for body fat estimate)

Age (years, for body fat estimate)

Height

Weight (lbs)

Waist Circumference (inches)

Your BMI

—

BMI Scale

16 18.5 25 30 35 40

BMI Prime

—

BMI ÷ 25 (upper healthy limit)

Ponderal Index

—

Weight (kg) ÷ Height³ (m³)

Est. Body Fat %

—

Deurenberg formula (BMI, age, gender)

Waist-to-Height Ratio

—

Waist ÷ Height (both in same unit)

Obesity Classification

—

WHO / CDC classification

Results may vary. Always verify. Consult your healthcare provider for personalized medical advice.

BMI Category Reference — WHO & CDC Standard

Category	BMI Range (kg/m²)	Notes
Underweight	Below 18.5	May indicate nutritional deficiency
Normal Weight	18.5 – 24.9	Healthy range for most adults
Overweight	25.0 – 29.9	Elevated risk of weight-related conditions
Obese — Class I	30.0 – 34.9	High risk — lifestyle changes recommended
Obese — Class II	35.0 – 39.9	Very high risk — medical consultation advised
Obese — Class III	40.0 and above	Severe/morbid obesity — immediate medical attention

Category

BMI Range (kg/m²)

Notes

Underweight

Below 18.5

May indicate nutritional deficiency

Normal Weight

18.5 – 24.9

Healthy range for most adults

Overweight

25.0 – 29.9

Elevated risk of weight-related conditions

Obese — Class I

30.0 – 34.9

High risk — lifestyle changes recommended

Obese — Class II

35.0 – 39.9

Very high risk — medical consultation advised

Obese — Class III

40.0 and above

Severe/morbid obesity — immediate medical attention

How to Use the BMI Calculator

Choose Imperial or Metric

Select your preferred unit system at the top of the form. Imperial uses pounds, feet, and inches — the standard in the US. Metric uses kilograms and centimetres — used internationally. All fields and results update automatically to match your selection.

Enter Your Details

Select your gender and enter your age, height, weight, and waist circumference. Height and weight are the only fields required for your BMI number. Age and gender are used to calculate your estimated body fat percentage using the Deurenberg formula. Waist circumference is used for the waist-to-height ratio.

Press Calculate and Read Your Results

Click Calculate BMI. Your results appear instantly — your BMI number, color-coded gauge showing where you fall on the scale, weight category, healthy weight range for your height, BMI Prime, Ponderal Index, estimated body fat percentage, and waist-to-height ratio.

Interpret and Act on Your Results

Use the results as a general health screening tool, not a medical diagnosis. BMI does not account for muscle mass, bone density, or body fat distribution. Athletes and highly muscular individuals may have a high BMI while being very healthy. Always consult your doctor for personalized health guidance.

Frequently Asked Questions

What is a healthy BMI range for adults?

What is BMI Prime and what does it mean?

What is the Ponderal Index and how is it different from BMI?

How accurate is the body fat percentage estimate?

What is waist-to-height ratio and why does it matter?

BMI Category Reference — WHO & CDC Standard

How to Use the BMI Calculator

Frequently Asked Questions

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