How to Calculate BMI by Hand (Formula in Imperial and Metric)
By Jorge Sanchez · April 20, 2026 · 5 min read
Bottom line: Imperial formula: BMI = (weight in lbs × 703) ÷ height in inches². A 5'6" (66 in) person at 150 lbs: (150 × 703) ÷ 66² = 105,450 ÷ 4,356 = 24.2 (Normal weight).
The BMI Formulas
Imperial (lbs / inches)
BMI = (lbs × 703) ÷ in²
Metric (kg / meters)
BMI = kg ÷ m²
Step-by-Step Calculation (Imperial)
Example: 5'10" tall, weighing 185 lbs
- Convert height to inches: 5 × 12 + 10 = 70 inches
- Square the height: 70 × 70 = 4,900
- Multiply weight by 703: 185 × 703 = 130,055
- Divide: 130,055 ÷ 4,900 = BMI 26.5 (Overweight)
Step-by-Step Calculation (Metric)
Example: 1.75 m tall, weighing 80 kg
- Square height: 1.75 × 1.75 = 3.0625 m²
- Divide weight by height²: 80 ÷ 3.0625 = BMI 26.1 (Overweight)
BMI Categories (WHO Standard)
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Normal weight |
| 25.0–29.9 | Overweight |
| 30.0–34.9 | Obese (Class I) |
| 35.0–39.9 | Obese (Class II) |
| 40.0 and above | Severely Obese (Class III) |
BMI Reference Chart by Height
Normal weight range (BMI 18.5–24.9) for common heights:
| Height | Normal Weight Range |
|---|---|
| 5'0" (152 cm) | 95–128 lbs (43–58 kg) |
| 5'4" (163 cm) | 108–145 lbs (49–65 kg) |
| 5'6" (168 cm) | 115–154 lbs (52–70 kg) |
| 5'9" (175 cm) | 125–169 lbs (57–77 kg) |
| 6'0" (183 cm) | 136–183 lbs (62–83 kg) |
| 6'2" (188 cm) | 144–194 lbs (65–88 kg) |
Limitations of BMI
BMI is a screening tool, not a diagnostic measure. It doesn't account for:
- Muscle mass: Athletes often have "overweight" BMI despite low body fat
- Age: Older adults can have "normal" BMI but excess visceral fat
- Sex: Women typically carry more body fat than men at the same BMI
- Ethnicity: Asian populations have higher health risks at lower BMI thresholds
- Distribution: Where fat is stored (belly vs. hips) matters more than total amount
BMI Calculator
Calculate your BMI in imperial or metric, with your category, healthy weight range, and body weight goal.
Calculate My BMI →Jorge Sanchez · Live Event Production Specialist · CalQpro