BMI Calculator
Enter your weight in pounds, height in inches, and age to calculate your BMI and see which category it falls into (Underweight, Normal, Overweight, or Obese). BMI is a commonly used screening tool — not a diagnostic measure — for assessing healthy weight ranges.
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Calculator
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Formula
BMI = 703 × Weight (lbs) ÷ Height² (inches)
The factor 703 converts the imperial units (pounds and inches) to match the metric BMI formula (kg/m²). Height is squared because BMI scales with area, not just one dimension. A BMI below 18.5 is underweight; 18.5-24.9 is normal; 25-29.9 is overweight; 30 and above is obese. Category codes: 1=Underweight, 2=Normal, 3=Overweight, 4=Obese.
How to use the BMI Calculator
- 1
Enter your weight (lbs)
- 2
Enter your height (inches)
- 3
Enter your age (years)
- 4
Read your results instantly
Results update in real time as you type.
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BMI Categories and Limitations
The four standard adult BMI categories established by the CDC are: Underweight (< 18.5), Normal weight (18.5-24.9), Overweight (25-29.9), and Obese (≥ 30). BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, age, or body fat distribution. Highly muscular people may have high BMIs despite low body fat. Consult a healthcare provider for a full health assessment.
BMI for Children and Teens
Adult BMI categories do not apply to children and teens (ages 2-19). For minors, BMI is plotted on age- and sex-specific growth charts, and results are expressed as percentiles rather than fixed cutoffs. A BMI at the 85th-94th percentile is overweight; at or above the 95th percentile is obese. This calculator uses adult category thresholds, so results for those under 20 should be interpreted with a pediatric chart.
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Beyond BMI: Other Health Indicators
Waist circumference is a complementary measure: a waist above 35 inches (women) or 40 inches (men) indicates increased metabolic risk regardless of BMI. Waist-to-height ratio (waist should be less than half your height) is gaining acceptance as a more accurate predictor than BMI alone. Body fat percentage measured by DEXA scan or bioelectrical impedance gives the most direct assessment of body composition.
Tips & Insights
Convert Height to Inches
Multiply feet by 12 and add remaining inches. 5 feet 8 inches = (5 × 12) + 8 = 68 inches. Enter 68 in the height field.
BMI Is a Starting Point, Not a Verdict
Athletes and bodybuilders routinely fall in the 'overweight' BMI range despite having low body fat. Consider waist circumference and other metrics alongside BMI.
Track Trends Over Time
A single BMI reading is less useful than tracking the trend. Consistent downward movement from 29 toward 24 over 6 months tells a much more meaningful story than a snapshot.
Worked Examples
Average Adult (160 lbs, 68 inches)
BMI = 24.3 (category 2: Normal weight).
Overweight Example (200 lbs, 68 inches)
BMI = 30.4 (category 4: Obese).
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Frequently Asked Questions
What is a healthy BMI?
For adults, 18.5-24.9 is the normal weight range. This corresponds to category 2 in this calculator's output.
Why is the formula different for pounds vs. kilograms?
The original metric formula is kg/m². The factor 703 converts pounds and inches to equivalent metric values.
Can BMI be inaccurate?
Yes. BMI overestimates body fat in muscular people and underestimates it in those with low muscle mass (e.g., elderly adults). It also does not indicate where fat is distributed, which matters clinically.
What is the BMI for my height?
Calculate the normal BMI weight range: 18.5 × height² ÷ 703 (lower) to 24.9 × height² ÷ 703 (upper). For 68 inches: 18.5 × 4624 ÷ 703 = 121.6 lbs to 24.9 × 4624 ÷ 703 = 163.7 lbs.
Is BMI the same for men and women?
The formula is the same, but men generally have more muscle mass and less body fat than women at the same BMI. Some researchers argue for sex-specific cut-offs, but standard clinical guidelines use the same thresholds for both.
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