BMI Calculator

Calculate your Body Mass Index (BMI) from height and weight. See your BMI category, healthy weight range, and understand what the number means for your health.

Feet portion
Inches portion
lbs
Weight in pounds
Your BMI Results
— BMI
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Under 18.518.5253040+
Category—
Healthy Weight Range—
BMI Prime—
Formula Used
BMI = (Weight ÷ Height²) × 703

Disclaimer: BMI is a screening tool, not a diagnostic measure. Consult a healthcare professional for medical advice.

What Is BMI?

Body Mass Index (BMI) is a numerical value calculated from a person's weight and height. It serves as a screening tool to categorize individuals into weight categories: underweight, normal weight, overweight, and obese. BMI applies to adults aged 20 and older regardless of sex.

BMI does not measure body fat directly. It uses a mathematical formula that correlates with body fat levels for most people. The formula was developed by Belgian mathematician Adolphe Quetelet in the 1830s and has been used as a public health metric since the 1970s.

BMI Formula

Imperial Formula
BMI = (Weight in pounds ÷ Height in inches²) × 703
Metric Formula
BMI = Weight in kilograms ÷ Height in meters²

BMI Categories

BMI RangeCategoryHealth Risk
Below 18.5UnderweightIncreased risk of nutritional deficiency
18.5 – 24.9Normal WeightLowest risk
25.0 – 29.9OverweightIncreased risk of chronic disease
30.0 – 34.9Obese (Class I)High risk
35.0 – 39.9Obese (Class II)Very high risk
40.0+Obese (Class III)Extremely high risk

BMI Calculation Examples

1
Example: 5'8", 150 lbsHeight = 68 inches. BMI = (150 ÷ 68²) × 703 = (150 ÷ 4,624) × 703 = 22.8 → Normal weight
2
Example: 5'4", 180 lbsHeight = 64 inches. BMI = (180 ÷ 64²) × 703 = (180 ÷ 4,096) × 703 = 30.9 → Obese (Class I)
3
Example: 6'0", 170 lbsHeight = 72 inches. BMI = (170 ÷ 72²) × 703 = (170 ÷ 5,184) × 703 = 23.1 → Normal weight

Limitations of BMI

  • Does not distinguish muscle from fat. Athletes and bodybuilders may have high BMI with low body fat.
  • Does not account for fat distribution. Abdominal fat (visceral fat) carries higher health risks than fat distributed elsewhere.
  • Age and sex differences. Women tend to have more body fat than men at the same BMI. Older adults may have more fat and less muscle.
  • Ethnic variations. BMI thresholds may differ for Asian, Pacific Islander, and other populations.

Important: BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, race, ethnicity, sex, or age. Always consult a healthcare professional for medical assessment.

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BMI Calculator FAQ

A healthy BMI range is 18.5 to 24.9. Below 18.5 is underweight. 25.0 to 29.9 is overweight. 30.0 and above is obese.
BMI = weight (lbs) ÷ height² (inches²) × 703. In metric: BMI = weight (kg) ÷ height² (m²).
BMI does not distinguish muscle from fat. Athletes with high muscle mass may have elevated BMI while having low body fat. Use body fat percentage alongside BMI.
BMI of 30.0 or higher. Class I: 30-34.9, Class II: 35-39.9, Class III: 40.0+.
Children use BMI-for-age percentiles. 85th-94th percentile is overweight, 95th+ is obese. Use CDC growth charts.
For adults 20+, the healthy range is 18.5-24.9 regardless of age. For adults over 65, BMI 23-30 may be slightly protective.
Caloric deficit, 150 min/week moderate exercise, strength training, adequate protein, and consistent sleep. Aim for 1-2 lbs loss per week.
No. BMI is weight-to-height ratio. Body fat % measures actual fat tissue. Same BMI can mean different body fat levels.

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